Analysis of information sources in references of the Wikipedia article "Putnam model" in English language version.
The special skills factor, B, is a function of system size: .16 for 5-15 KSLOC, .18 for 20 KSLOC, .28 for 30 KSLOC, .34 for 40 KSLOC, .37 for 50 KSLOC and .39 for > 70 KSLOC