“…The problem of nonlinear weighted LS and total least squares fitting of the Bass curve (2) is considered by Jukić (2013;2011). Results on the existence of the LS estimate for some other special classes of functions can be found in the works of Bates and Watts (1988), Björck (1996), Demidenko (2008;2006;, Hadeler et al (2007), Jukić (2013;2009), Jukić and, Jukić et al (2008;, Marković and Jukić (2010), as well as Marković et al (2009).…”