GouldW., PitbladoJ., and SribneyW.2003. Maximum Likelihood Estimation with Stata.2d ed. College Station, TX: Stata Press.
2.
JenkinsS. P.1999. sg106: Fitting Singh–Maddala and Dagum distributions by maximum likelihood. Stata Technical Bulletin48: 19–25. In Stata Technical Bulletin Reprints, vol. 8, 261–268. College Station, TX: Stata Press.