A machine learning approach to keystroke dynamics based user authentication

A statistical framework for evaluating neural networks to predict recurrent events in breast cancer
Gorunescu, F., Gorunescu, M., El-Darzi, E. and Gorunescu, S. 2010. A statistical framework for evaluating neural networks to predict recurrent events in breast cancer. International Journal of General Systems. 39 (5), pp. 471-488. https://doi.org/10.1080/03081079.2010.484282

Exploring the role of glycosylated hemoglobin as a marker for type 2 diabetes mellitus using rough sets
Revett, K. and Salem, A.B.M. 2010. Exploring the role of glycosylated hemoglobin as a marker for type 2 diabetes mellitus using rough sets. in: The 7th International Conference on Informatics and Systems (INFOS) IEEE . pp. 1-7

Introduction to behavioral biometrics
Revett, K. 2010. Introduction to behavioral biometrics. in: Jahankhani, H., Watson, D.L. and Gianuigi, L. (ed.) Handbook of electronic security and digital forensics World Scientific Publishing.

Bioinformatics and Biometrics
Revett, K. 2010. Bioinformatics and Biometrics. in: Jahankhani, H., Watson, D.L. and Gianuigi, L. (ed.) Handbook of electronic security and digital forensics World Scientific Publishing.

Patient grouping optimization using a hybrid self-organizing map and Gaussian mixture model for length of stay-based clustering system
Gorunescu, F., Belciug, S., El-Darzi, E. and Gorunescu, M. 2010. Patient grouping optimization using a hybrid self-organizing map and Gaussian mixture model for length of stay-based clustering system. in: 5th IEEE International Conference on Intelligent Systems (IS 2010) proceedings IEEE . pp. 173-178

Modeling the Listeria monocytogenes survival/death curves using wavelet neural networks
Amina, M., Kodogiannis, V., Revett, K. and Lygouras, J.N. 2010. Modeling the Listeria monocytogenes survival/death curves using wavelet neural networks. in: 2010 International Joint Conference on Neural Networks (IJCNN), Barcelona, Spain, 18-23 July 2010 IEEE . pp. 1-8

A bioinformatics based approach to user authentication via keystroke dynamics
Revett, K. 2009. A bioinformatics based approach to user authentication via keystroke dynamics. International Journal of Control, Automation and Systems. 7 (1), pp. 7-15. https://doi.org/10.1007/s12555-009-0102-2

Keystroke dynamic and graphical authentication systems
Tenreiro de Magalhaes, S., Santos, L.D., Revett, K. and Santos, H.M.D. 2009. Keystroke dynamic and graphical authentication systems. in: Khosrow-Pour, M. (ed.) Encyclopedia of information science and technology. 2nd edition Hershey, Pa. ; London Information Science.

Using technology to overcome the password's contradiction
Tenreiro de Magalhaes, S., Revett, K., Santos, H.M.D., Santos, L.D., Oliveira, A. and Ariza, C. 2009. Using technology to overcome the password's contradiction. in: Gupta, M. and Sharman, R. (ed.) Handbook of research on social and organizational liabilities in information security Hershey, Pa. ; London Information Science Reference.

Usage of artificial intelligent technology in healthy food planning for people with disabilities
Sicurello, F., Salem, A.B.M., De Luca, A.R., Stenta, U., Amon, T. and Revett, K. 2009. Usage of artificial intelligent technology in healthy food planning for people with disabilities. EMMIT 2009: Euro-Mediterranean Medical Informatics and Telemedicine, 5th International Conference. Beirut, Lebanon 16 - 18 Oct 2009

Machine learning techniques in electrocardiogram diagnosis
Salem, A.B.M., Revett, K. and El-Dahshan, E.S. 2009. Machine learning techniques in electrocardiogram diagnosis. Fourth International Conference on Intelligent Computing and Information Systems (ICICIS 2009). Cairo, Egypt 18 - 22 Mar 2009 pp. 260-264

A rule-based approach to processing SPECT imaging for the diagnosis of heart disease
Revett, K., Salem, A.B.M. and Gorunescu, F. 2009. A rule-based approach to processing SPECT imaging for the diagnosis of heart disease. EMMIT 2009: Euro-Mediterranean Medical Informatics and Telemedicine, 5th International Conference. Beirut, Lebanon 16 - 18 Oct 2009

Evaluation of the feature space of an erythematosquamous dataset using rough sets
Revett, K., Gorunescu, F., Salem, A.B.M. and El-Dahshan, E.S. 2009. Evaluation of the feature space of an erythematosquamous dataset using rough sets. Annals of the University of Craiova - Mathematics and Computer Science Series. 36 (2), pp. 123-130.

Feature selection in Parkinson's disease: a rough sets approach
Revett, K., Gorunescu, F. and Salem, A.B.M. 2009. Feature selection in Parkinson's disease: a rough sets approach. in: Proceedings of the International Multiconference on Computer Science and Information Technology 12 - 14 Oct 2009, Mragowo, Poland IMCSIT.

A machine learning approach to artefact extraction from independent components derived from EEG datasets
Revett, K., Gorunescu, F., El-Dahshan, E.S. and Salem, A.B.M. 2009. A machine learning approach to artefact extraction from independent components derived from EEG datasets. Fourth International Conference on Intelligent Computing and Information Systems (ICICIS 2009). Cairo, Egypt 18 - 22 Mar 2009 pp. 184-189

Machine learning in electrocardiogram diagnosis
Revett, K., Gorunescu, F., El-Dahshan, E.S. and Salem, A.B.M. 2009. Machine learning in electrocardiogram diagnosis. in: Proceedings of the International Multiconference on Computer Science and Information Technology 12 - 14 Oct 2009, Mragowo, Poland IMCSIT.

Current trends in behavioral biometrics, keynote speech
Revett, K. 2009. Current trends in behavioral biometrics, keynote speech. Fourth International Conference on Intelligent Computing and Information Systems (ICICIS 2009). Cairo, Egypt 18 - 22 Mar 2009 pp. 42-48

Behavioral biometrics: a biosignal based approach
Revett, K. 2009. Behavioral biometrics: a biosignal based approach. in: Wang, L. and Geng, X. (ed.) Behavioral biometrics for human identification: intelligent applications Hershey, PA Medical Information Science Reference. pp. 101-120

Length of stay-based clustering methods for patient grouping
El-Darzi, E., Abbi, R., Vasilakis, C., Gorunescu, F., Gorunescu, M. and Millard, P.H. 2009. Length of stay-based clustering methods for patient grouping. in: McClean, S.I., Millard, P.H., El-Darzi, E. and Nugent, C. (ed.) Intelligent patient management Berlin Heidelberg Springer.

A survey of user authentication based on mouse dynamics
Revett, K., Jahankhani, H., Tenreiro de Magalhaes, S. and Santos, H.M.D. 2008. A survey of user authentication based on mouse dynamics. in: Jahankhani, H., Revett, K. and Palmer-Brown, D. (ed.) Global e-security: 4th International Conference, ICGeS 2008, London, UK, June 23-25, 2008. Proceedings Berlin / Heidelberg Springer.

User dynamics in graphical authentication systems
Revett, K., Jahankhani, H., Tenreiro de Magalhaes, S. and Santos, H.M.D. 2008. User dynamics in graphical authentication systems. in: Jahankhani, H., Revett, K. and Palmer-Brown, D. (ed.) Global e-security: 4th International Conference, ICGeS 2008, London, UK, June 23-25, 2008. Proceedings Berlin / Heidelberg Springer.

An automated predictor of hydrogen gas production from a sucrose based bioreactor system
Revett, K., Gorunescu, F., Gorunescu, M., Nikhil and Ozkaya, B. 2008. An automated predictor of hydrogen gas production from a sucrose based bioreactor system. in: Proceedings of the 8th International Conference on Artificial Intelligence and Digital Communications - AIDC’08 Craiova Universitaria Publishing House. pp. 161-170

A machine learning investigation of a beta-carotenoid dataset
Revett, K. 2008. A machine learning investigation of a beta-carotenoid dataset. in: Bello, R., Falcón, R., Pedrycz, W. and Kacprzyk, J. (ed.) Granular computing: at the junction of rough sets and fuzzy sets Berlin / Heidelberg Springer.

Diagnostic feature analysis of a dobutamine stress echocardiography dataset using rough sets
Revett, K. 2008. Diagnostic feature analysis of a dobutamine stress echocardiography dataset using rough sets. in: Transactions on rough sets IX Berlin, Heidelberg Springer.

Behavioral biometrics: a remote access approach
Revett, K. 2008. Behavioral biometrics: a remote access approach. Chichester Wiley.

A rule based approach to classification of EEG datasets: a comparison between ANFIS and rough sets
Jahankhani, P., Revett, K. and Kodogiannis, V. 2008. A rule based approach to classification of EEG datasets: a comparison between ANFIS and rough sets. in: Reljin, B. and Stankovic, S. (ed.) Proceedings of the Ninth Symposium on Neural Network Applications in Electrical Engineering: NEUREL 2008, September 27-28, 2008, Faculty of Electrical Engineering, University of Belgrade Los Alamitos, USA IEEE . pp. 157-160

Classification using adaptive fuzzy inference neural networks
Jahankhani, P., Kodogiannis, V., Revett, K. and Lygouras, J.N. 2008. Classification using adaptive fuzzy inference neural networks. in: Proceedings of the Twelfth IASTED International Conference on Artificial Intelligence and Soft Computing, September 1-3 2008, Palma de Mallorca, Spain Acta Press. pp. 1-6

A statistical evaluation of neural computing approaches to predict recurrent events in breast cancer
Gorunescu, F., Gorunescu, M., El-Darzi, E. and Gorunescu, S. 2008. A statistical evaluation of neural computing approaches to predict recurrent events in breast cancer. in: Proceedings of the 4th International IEEE Conference on Intelligent Systems IS'08. Varna, Bulgaria, September, 6-8 2008 Los Alamitos, USA IEEE .

Information technologies for the information agent
Tenreiro de Magalhaes, S., Santos, H.M.D., Santos, L.D., Revett, K. and Nunes, P.V. 2007. Information technologies for the information agent. in: Remenyi, D. (ed.) Proceedings of the 6th European Conference on Information Warfare and Security, Defence College of Management and Technology, Shrivenham, UK, 2-3 July 2007 Reading Academic Conferences. pp. 273-280

Examination of the parameter space of a computational model of acute ischaemic stroke using rough sets
Revett, K. 2007. Examination of the parameter space of a computational model of acute ischaemic stroke using rough sets. in: Rough Sets and Knowledge Technology: second international conference, RSKT 2007 Toronto, Canada, May 2007 proceedings Berlin, Germany Springer.

Data mining an EEG dataset with an emphasis on dimensionality reduction
Jahankhani, P., Revett, K. and Kodogiannis, V. 2007. Data mining an EEG dataset with an emphasis on dimensionality reduction. in: IEEE Symposium on Computational Intelligence and Data Mining (CIDM), 01-05 Apr 2007, Honolulu, Hawaii, USA Los Alamitos, USA IEEE . pp. 405-412

Digital anti forensics: tools and approaches
Jahankhani, H., Anastasios, B. and Revett, K. 2007. Digital anti forensics: tools and approaches. in: Remenyi, D. (ed.) Proceedings of the 6th European Conference on Information Warfare and Security, Defence College of Management and Technology, Shrivenham, UK, 2-3 July 2007 Reading Academic Conferences. pp. 115-120

Keystroke dynamics - stepping forward in authentication
Tenreiro de Magalhaes, S., Revett, K. and Santos, H.M.D. 2006. Keystroke dynamics - stepping forward in authentication. GESTS International Transactions on Computer Science and Engineering. 29 (1), pp. 113-119.

Critical aspects in authentication graphic keys
Tenreiro de Magalhaes, S., Santos, H.M.D. and Revett, K. 2006. Critical aspects in authentication graphic keys. in: Proceedings of the 1st International Conference on Information Warfare and Security - 2006 Kidmore End, England Academic Conferences and Publishing International. pp. 212-217

Generation of authentication strings from graphic keys
Tenreiro de Magalhaes, S., Revett, K. and Santos, H.M.D. 2006. Generation of authentication strings from graphic keys. International Journal of Computer Science and Network Security. 63, p. 38.

Enhancing login security through the use of keystroke input dynamics
Revett, K., Tenreiro de Magalhaes, S. and Santos, H.M.D. 2006. Enhancing login security through the use of keystroke input dynamics. in: Zhang, D. and Jain, A.K. (ed.) Advances in Biometrics: International Conference, ICB 2006, Hong Kong, China, January 5-7, 2006: Proceedings Berlin, Germany Springer.

Attribute selection for EEG signal classification using rough sets and neural networks
Revett, K., Szczuka, M., Jahankhani, P. and Kodogiannis, V. 2006. Attribute selection for EEG signal classification using rough sets and neural networks. in: Greco, S., Hata, Y., Hirano, S., Inuiguchi, M., Miyamoto, S., Nguyen, H.S. and Slowinski, R. (ed.) Rough sets and current trends in computing: 5th international conference, RSCTC 2006, Kobe, Japan, November 6-8, 2006: proceedings Berlin, Germany Springer.

Authenticating computer access based on keystroke dynamics using a probabilistic neural network
Revett, K., Gorunescu, F., Gorunescu, M., Ene, M., Tenreiro de Magalhaes, S. and Santos, H.M.D. 2006. Authenticating computer access based on keystroke dynamics using a probabilistic neural network. in: 2nd International Conference on Global E-Security, London, UK, 20-22 April 2006 (ICGeS-06) UNKNOWN. pp. 65-71

A machine learning approach to differentiating bacterial from viral meningitis
Revett, K., Gorunescu, F., Gorunescu, M. and Ene, M. 2006. A machine learning approach to differentiating bacterial from viral meningitis. in: IEEE John Vincent Atanasoff 2006 International Symposium on Modern Computing (JVA'06) Los Alamitos, USA IEEE . pp. 155-162

EEG signal classification using wavelet feature extraction and neural networks
Jahankhani, P., Kodogiannis, V. and Revett, K. 2006. EEG signal classification using wavelet feature extraction and neural networks. in: JVA '06. IEEE John Vincent Atanasoff 2006 International Symposium on Modern Computing, 2006. Los Alamitos, USA IEEE . pp. 120-124

A neural computing-based approach for the early detection of hepatocellular carcinoma
Gorunescu, M., Gorunescu, F. and Revett, K. 2006. A neural computing-based approach for the early detection of hepatocellular carcinoma. International Journal of Biomedical Sciences. 1 (4), pp. 255-258.

Automatically building 2D statistical shapes using the topology preservation model GNG
Garcia Rodriguez, J., Angelopoulou, A., Psarrou, A. and Revett, K. 2006. Automatically building 2D statistical shapes using the topology preservation model GNG. in: Narayanan, P.J., Nayar, S.K. and Shum, H.Y. (ed.) Computer Vision ACCV 2006: 7th Asian Conference on Computer Vision, Hyderabad, India, January 13-16, 2006: Proceedings, Part I Springer.

A rough set-based magnetic resonance imaging partial volume detection system
Widz, S., Revett, K. and Slezak, D. 2005. A rough set-based magnetic resonance imaging partial volume detection system. in: Pal, S.K., Bandyopadhyay, S. and Biswas, S. (ed.) Pattern Recognition and Machine Intelligence: First International Conference, PReMI 2005, Kolkata, India, December 20-22, 2005: Proceedings Berlin, Germany Springer.

A hybrid approach to MR imaging segmentation using unsupervised clustering and approximate reducts
Widz, S., Revett, K. and Slezak, D. 2005. A hybrid approach to MR imaging segmentation using unsupervised clustering and approximate reducts. in: Slezak, D., Yao, J., Peters, J.F., Ziarko, W. and Hu, X. (ed.) Rough Sets, Fuzzy Sets, Data Mining, and Granular Computing: 10th International Conference, RSFDGrC 2005, Regina, Canada, August 31 - September 3, 2005: Proceedings Springer Berlin, Germany.

Password secured sites: stepping forward with keystroke dynamics
Tenreiro de Magalhaes, S., Revett, K. and Santos, H.M.D. 2005. Password secured sites: stepping forward with keystroke dynamics. in: International Conference on Next Generation Web Services Practices, 2005: NWeSP 2005 USA IEEE . pp. 293-298

Generalized net model with intuitionistic fuzzy estimations of the process of obtaining of scientific titles and degrees
Shannon, A., Riecan, B., Langova-Orozova, D., El-Darzi, E., Kerre, E., Sotirova, E., Gorunescu, F., Petrounias, I., Trelewicz, J., Atanassov, K.T., Krawczak, M., Chountas, P., Melo-Pinto, P., Georgiev, P., Kim, T. and Tasseva, V. 2005. Generalized net model with intuitionistic fuzzy estimations of the process of obtaining of scientific titles and degrees. Notes on Intuitionistic Fuzzy Sets. 11, pp. 95-114.

DataMining a keystroke dynamics biometrics database using rough sets
Revett, K., Tenreiro de Magalhaes, S. and Santos, H.M.D. 2005. DataMining a keystroke dynamics biometrics database using rough sets. in: Cardoso, A., Bento, C. and Dias, G. (ed.) EPIA05: 12th Portuguese Conference on Artificial Intelligence New York, USA IEEE . pp. 188-191

A rough sets based breast cancer decision support system
Revett, K. and Khan, A. 2005. A rough sets based breast cancer decision support system. in: Proceedings of the 2005 International Conference on Mathematics and Engineering Techniques in Medicine and Biological Sciences (METMBS '05). June 20 - 23, 2005, Monte Carlo Resort, Las Vegas, Nevada, USA CSREA Press. pp. 194-199

SOM based image pathology detection system
Revett, K. and Khan, A. 2005. SOM based image pathology detection system. in: Isai­as, P., Nunes, M.B. and Palma dos Reis, A. (ed.) Proceedings of the IADIS Virtual Multi Conference on Computer Science and Information Systems (MCCSIS 2005), April 11 - 29, 2005 IADIS. pp. 213-216

Enhancing login security using keystroke hardening and keyboard gridding
Revett, K. and Khan, A. 2005. Enhancing login security using keystroke hardening and keyboard gridding. in: Isai­as, P., Nunes, M.B. and Palma dos Reis, A. (ed.) Proceedings of the IADIS Virtual Multi Conference on Computer Science and Information Systems (MCCSIS 2005), April 11 - 29, 2005 IADIS. pp. 471-475

Classifying heart disease datasets using rough sets
Revett, K. and Khan, A. 2005. Classifying heart disease datasets using rough sets. in: Proceedings of the 2005 International Conference on Mathematics and Engineering Techniques in Medicine and Biological Sciences (METMBS '05). June 20 - 23, 2005, Monte Carlo Resort, Las Vegas, Nevada, USA CSREA Press.

A breast cancer diagnosis system: a combined approach using rough sets and probabilistic neural networks
Revett, K., Gorunescu, F., Gorunescu, M., El-Darzi, E. and Ene, M. 2005. A breast cancer diagnosis system: a combined approach using rough sets and probabilistic neural networks. in: EUROCON 2005: the International Conference on "Computer as a Tool": Belgrade, Serbia and Montenegro, November 21-24 2005 London, UK IEEE .

Attribute extraction and classification using rough sets on a lymphoma dataset
Revett, K. and Aydin, N. 2005. Attribute extraction and classification using rough sets on a lymphoma dataset. in: Proceedings of the 1st International Symposium on Health Informatics and Bioinformatics: HIBIT'05, 10-12 Nov 2005, Antalya, Turkey HIBIT.

A rough sets based classifier for primary biliary cirrhosis
Revett, K. 2005. A rough sets based classifier for primary biliary cirrhosis. in: EUROCON 2005: The International Conference on "Computer as a Tool": Belgrade, Serbia and Montenegro, November 21-24 2005 USA IEEE .

A computational model of stroke-in-progression
Revett, K. 2005. A computational model of stroke-in-progression. 14th Annual Meeting of the Computational Neuroscience Society (CNS2005). Madison, USA 17-21 Jul 2005

A computational model of acute and delayed tissue damage resulting from ischemic stroke
Revett, K. 2005. A computational model of acute and delayed tissue damage resulting from ischemic stroke. Fourteenth Annual Computational Neuroscience Meeting (CNS2005). Madison, USA 17-21 Jul 2005

Developing a keystroke dynamics based agent using rough sets
Revett, K. 2005. Developing a keystroke dynamics based agent using rough sets. in: 2005 IEEE/WIC/ACM International Joint Conference on Web Intelligence and Intelligent Agent Technology Compiegne, France University of Compiegne.

Apoptosis as a mediator of delayed tissue damage in progressive stroke: a computational study
Revett, K. 2005. Apoptosis as a mediator of delayed tissue damage in progressive stroke: a computational study. in: Proceedings of the Annual Meeting of the International Society for Computational Biology (ISMB 2005), 25-29 Jun 2005, Detroit, USA. International Society for Computational Biology.

Computational modelling of the gene expression profile from acute ischaemic brain injury
Kola, J. and Revett, K. 2005. Computational modelling of the gene expression profile from acute ischaemic brain injury. in: 2005 ICSC Congress on Computational Intelligence Methods and Applications USA IEEE .

Data mining a hepatitis dataset using rough sets
Khan, A. and Revett, K. 2005. Data mining a hepatitis dataset using rough sets. in: AIDC 2005: International Conference on Artificial Intelligence and Digital Communications UNKNOWN. pp. 12-20

An automated anomaly EEG detection algorithm using discrete wavelet transforms
Jahankhani, P., Revett, K., Spackman, L., Kodogiannis, V. and Boyd, S. 2005. An automated anomaly EEG detection algorithm using discrete wavelet transforms. in: Prasad, B. (ed.) Proceedings of the 2nd Indian International Conference on Artificial Intelligence, Pune, India, December 20-22, 2005 (IICAI 05) IICAI. pp. 2679-2685

Detecting clinically relevant EEG anomalies using discrete wavelet transforms
Jahankhani, P., Revett, K. and Kodogiannis, V. 2005. Detecting clinically relevant EEG anomalies using discrete wavelet transforms. in: Proceedings of the 5th WSEAS International Conference on Wavelet Analysis and Multirate Systems (WAMUS 2005). Sofia, Bulgaria, 27 - 29 Oct 2005 WSEAS.

Automatic detection Of EEG abnormalities using wavelet transformations
Jahankhani, P., Revett, K. and Kontogiannis, V. 2005. Automatic detection Of EEG abnormalities using wavelet transformations. WSEAS Transactions on Signal Processing. 1 (1), pp. 55-60.

A heuristic approach in hepatic cancer diagnosis using a probabilistic neural network-based model
Gorunescu, M., Gorunescu, F., Ene, M. and El-Darzi, E. 2005. A heuristic approach in hepatic cancer diagnosis using a probabilistic neural network-based model. in: Janssen, J. and Lenca, P. (ed.) Applied Stochastic Models and Data Analysis Brest, France ENST Bretagne. pp. 1016-1025

A hybrid approach to cancer classification: rough sets and probabilistic neural networks
Gorunescu, F., Gorunescu, M., El-Darzi, E., Gorunescu, S., Revett, K. and Khan, A. 2005. A hybrid approach to cancer classification: rough sets and probabilistic neural networks. in: The First East European Conference on Health Care Modelling and Computation (HCMC 2005). Craiova, Romania, August 31st - September 2nd, 2005 Craiova, Romania Universitatea din Craiova. pp. 149-159

An evolutionary computational approach to probabilistic neural network with application to hepatic cancer diagnosis
Gorunescu, F., Gorunescu, M., El-Darzi, E. and Gorunescu, S. 2005. An evolutionary computational approach to probabilistic neural network with application to hepatic cancer diagnosis. in: Tsymbal, A. and Cunningham, P. (ed.) 18th IEEE Symposium on Computer-Based Medical Systems, 2005: proceedings USA IEEE . pp. 461-466

Animal toxins: what features differentiate pore blockers from gate modifiers
Bhogal, S. and Revett, K. 2005. Animal toxins: what features differentiate pore blockers from gate modifiers. in: 2005 ICSC Congress on Computational Intelligence Methods and Applications USA IEEE .

Verification of data in staging schema, mapping between source tables and materialized views
Ahmed, E. and Revett, K. 2005. Verification of data in staging schema, mapping between source tables and materialized views. in: Cardoso, A., Bento, C. and Dias, G. (ed.) EPIA05: 12th Portuguese Conference on Artificial Intelligence IEEE . pp. 200-204

Using a queueing model to help plan bed allocation in a department of geriatric medicine
Gorunescu, F., McClean, S.I. and Millard, P.H. 2002. Using a queueing model to help plan bed allocation in a department of geriatric medicine. Health Care Management Science. 5 (4), pp. 307-312. https://doi.org/10.1023/A:1020342509099

A queueing model for bed-occupancy management and planning of hospitals
Gorunescu, F., McClean, S.I. and Millard, P.H. 2002. A queueing model for bed-occupancy management and planning of hospitals. Journal of the Operational Research Society. 53 (1), pp. 19-24.