initial.values: NULL or a numeric vector with the initial parameter values passed on to the optimisation routine, nlminb. If NULL, the default, then the values are chosen automatically
lower: numeric vector, either of length 1 or the number of parameters to be estimated, see nlminb
upper: numeric vector, either of length 1 or the number of parameters to be estimated, see nlminb
method: an integer that determines the expression for the coefficient-covariance, see "details"
lag.length: NULL or an integer that determines the lag-length used in the robust coefficient covariance. If lag.length is an integer, then it is ignored unless method = 3
control: a list passed on to the control argument of nlminb
eps.tol: numeric, a small value that ensures the fitted zero-probabilities are not too small when the log-transformation is applied when computing the log-likelihood
solve.tol: numeric value passed on to the tol argument of solve, which is called whenever the coefficient-coariance matrix is computed. The value controls the toleranse for detecting linear dependence between columns when inverting a matrix