Reference

All functions
nls.lm()	Addresses NLS problems with the Levenberg-Marquardt algorithm
nls.lm.control()	Control various aspects of the Levenberg-Marquardt algorithm
nlsLM()	Standard 'nls' framework that uses 'nls.lm' for fitting
wfct()	Weighting function that can be supplied to the weights argument of nlsLM or nls