S. Didar-Al-Alam, S. Shahnewaz, D. Pfahl, and G. Ruhe. Product-Focused Software Process Improvement, volume 8892 of Lecture Notes in Computer Science, Springer International Publishing, (2014)
P. Abrahamsson, and J. Koskela. Empirical Software Engineering, 2004. ISESE '04. Proceedings. 2004 International Symposium on, page 73--82. (August 2004)