To cite the nlmeU package in publications use:
Andrzej Galecki & Tomasz Burzykowski (2013) Linear Mixed-Effects Models Using R: A Step-by-Step Approach First Edition. Springer, New York. ISBN 978-1-4614-3899-1
Corresponding BibTeX entry:
@Book{, title = {Linear Mixed-Effects Models Using R: A Step-by-Step Approach}, author = {Andrzej Galecki and Tomasz Burzykowski}, publisher = {Springer}, edition = {First}, address = {New York}, year = {2013}, note = {ISBN 978-1-4614-3899-1}, url = {http://www-personal.umich.edu/~agalecki}, }