TMDPSN = Total Effort Perceived to be still needed to complete the project (Man-Days)
MDRM = Total Effort remaining current plan (Man-Days)" (Abdel-Hamid and Madnick 1991; Abdel-Hamid 1984)
Also (Madachy 2008)
Abdel-Hamid, Tarek K. 1984. “The Dynamics of Software Development Project Management: An Integrative System Dynamics Perspective.” Ph.D., Massachusetts Institute of Technology. http://dspace.mit.edu/handle/1721.1/38235.
Abdel-Hamid, Tarek K., and Stuart E. Madnick. 1991. Software Project Dynamics: An Integrated Approach. Prentice Hall PTR.
Madachy, Raymond J. 2008. Software Process Dynamics. 28th ed. Wiley-IEEE Press.