H. C. Benestad, B. C. Anda, and E. Arisholm, Understanding software mainten-ance and evolution by analyzing individual changes: A literature review, Journal of Software Maintenance and Evolution: Research and Practice, 2009.
DOI : 10.1002/smr.412

B. Boehm and K. Sullivan, Software economics: status and prospects, Information and Software Technology, vol.41, issue.14, pp.937-946, 1999.
DOI : 10.1016/S0950-5849(99)00091-9
URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.589.2033

F. P. Brooks, No Silver Bullet Essence and Accidents of Software Engineering, Computer, vol.20, issue.4, pp.10-19, 1987.
DOI : 10.1109/MC.1987.1663532

N. Chapin, Software maintenance types-a fresh view, Proceedings International Conference on Software Maintenance ICSM-94, pp.247-252, 2000.
DOI : 10.1109/ICSM.2000.883056

. M. Davidsen and J. Krogstie, A longitudinal study of development and maintenance Information and Software Technology, pp.707-719, 2010.

. M. Davidsen and J. Krogstie, Information Systems Evolution over the Last 15 Years, Proceedings of CAiSE'2010, 2010.
DOI : 10.1007/978-3-642-13094-6_24

L. S. Flak, W. Dertz, A. Jansen, J. Krogstie, S. Ølnes et al., What is the Value of eGovernment -and How can we actually realize it. Transforming Government: People, Process and Policy, vol.3, issue.3, pp.220-226, 2009.

A. Følstad, H. Jørgensen, and J. Krogstie, User Involvement in e-Government Development Projects. Paper presented at the NordiChi, 2004.

J. Galtung, Theory and Method of Social Research, 1967.

A. Gupta, The Profile of Software Changes in Reused vs. Non-reused Industrial Software Systems Doctoral Thesis, p.90, 2009.

A. Gupta, O. P. Slyngstad, R. Conradi, P. Mohagheghi, H. Rønneberg et al., An Empirical Study of Software Changes in Statoil ASA - Origin, Priority Level and Relation to Component Size, 2006 International Conference on Software Engineering Advances (ICSEA'06), p.12, 2006.
DOI : 10.1109/ICSEA.2006.261268

R. Heeks, Implementing and Managing eGovernment, Sage, 2006.

K. K. Holgeid, J. Krogstie, and D. I. Sjøberg, A study of development and maintenance in Norway: assessing the efficiency of information systems support using functional maintenance, Information and Software Technology, vol.42, issue.10, pp.687-700, 2000.
DOI : 10.1016/S0950-5849(00)00111-7

C. Jones, The Economics of Software Maintenance in the Twenty First Century http, 2006.

M. Jørgensen, Empirical Studies of Software Maintenance, Research Report, vol.188, 1994.

B. A. Kitchenham, S. L. Pfleeger, L. M. Pickard, P. W. Jones, D. C. Hoaglin et al., Preliminary guidelines for empirical research in software engineering, IEEE Transactions on Software Engineering, vol.28, issue.8, pp.721-734, 2002.
DOI : 10.1109/TSE.2002.1027796
URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.118.3932

J. Krogstie and A. Sølvberg, Software maintenance in Norway: a survey investigation, Proceedings International Conference on Software Maintenance ICSM-94, pp.304-313, 1994.
DOI : 10.1109/ICSM.1994.336764

J. Krogstie, Use of methods and CASE-tools in Norway: Results from a survey, Journal of Automated Software Engineering, vol.3, pp.347-367, 1996.

J. Krogstie, On the distinction between functional development and functional maintenance, Journal of Software Maintenance: Research and Practice, vol.10, issue.6, pp.383-403, 1995.
DOI : 10.1145/356725.356731

J. Krogstie, A. Jahr, and D. I. , Sjøberg: A Longitudinal Study of Development and Maintenance in Norway, Report from the 2003 Investigation, Information and Software Technology, pp.993-1005, 2006.

J. Krogstie, Work distribution, Methodology, and Technology for ISD and Mainten-ance: Trends over the last 30 years, pp.131-142, 2006.
DOI : 10.1007/978-0-387-34732-5_13
URL : http://sedici.unlp.edu.ar/bitstream/handle/10915/24436/Documento_completo.pdf?sequence=1

K. Moløkken-Østvold, Effort and schedule estimation of software development projects, 2004.

M. Lee and T. L. Jefferson, An empirical study of software maintenance of a Web-based Java application, 21st IEEE International Conference on Software Maintenance (ICSM'05), 2005.
DOI : 10.1109/ICSM.2005.19

M. M. Lehman, Laws of Software Evolution Revisited LNCS 1149, pp.9-11, 1996.
DOI : 10.1007/bfb0017737
URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.39.4491

B. P. Lientz, E. B. Swanson, and G. E. Tompkins, Characteristics of application software maintenance, Communications of the ACM, vol.21, issue.6, pp.466-471, 1978.
DOI : 10.1145/359511.359522
URL : http://www.dtic.mil/get-tr-doc/pdf?AD=ADA034085

B. P. Lientz and E. B. Swanson, Software Maintenance Management, 1980.

J. T. Nosek and P. Palvia, Software maintenance management: Changes in the last decade, Journal of Software Maintenance: Research and Practice, vol.24, issue.3, pp.157-174, 1990.
DOI : 10.1002/smr.4360020303

V. T. Rajlich and K. H. Bennett, A staged model for the software life cycle, Computer, vol.33, issue.7, pp.66-71, 2000.
DOI : 10.1109/2.869374

M. Saunders, P. Lewis, and A. Thornhill, Research methods for business students, 2009.

S. R. Schach, B. Jin, L. Yu, G. Z. Heller, and J. Offutt, Determining the Distribution of Maintenance Categories: Survey versus Measurement, Empirical Software Engineering, vol.8, issue.4, pp.351-365, 2003.
DOI : 10.1023/A:1025368318006

H. Sousa and H. Moreira, A survey on the Software Maintenance Process, Proceedings. International Conference on Software Maintenance (Cat. No. 98CB36272), pp.268-274, 1998.
DOI : 10.1109/ICSM.1998.738518