Changes in version 1.0 (2021-08-20)                   

    o   Documentation was updated. The current version accompanies the publication in the 
	Journal of Statistical Software, <doi:10.18637/jss.v099.i04> 

                  Changes in version 0.8 (2020-04-02)                   

    o   Data argument was added for functions ssmrob, heckitrob, heckit5rob and etregrob.

    o   The datasets were updated: binary variables are logical now. 
	Several variables with missing documentation were removed from MEPS2001 dataset. 
	Documentation for datasets was updated.

    o   Computation of the (co)variance matrix for the estimator was made more efficient.

    o   NAMESPACE was updated: instead of package namespaces (MASS, robustbase, sampleSelection)
	only the necessary functions are imported.

                  Changes in version 0.7 (2019-07-19)                   

    o   Generic functions nobs and model.matrix were added.

    o   print and summary outputs were adjusted to mimic more standard R model printing outputs.

    o   fitted model objects were extended, see documentation.

                  Changes in version 0.6 (2019-05-16)                   

    o   Order of arguments in functions ssmrob, heckitrob, heckit5rob, etregrob was  
	changed. The selection formula is first, the outcome formula(s) is second.

                  Changes in version 0.5 (2018-12-09)                   

    o   Number of digits after comma in print functions reduced to 4.

    o   Chi-square probability for covariate weights is 0.95, it was 0.9.

    o   Splitted weight calculation for design space is introduced (see Zhelonkin, 		
	Genton, Ronchetti 2016, p.814).

    o   etregrob function is added, robust estimation for Endogenous Treatment Model.