To cite package 'lfe' in publications use:
Simen Gaure (2013) lfe: Linear Group Fixed Effects. R package version 1.4-963.
Corresponding BibTeX entry:
@Manual{,
title = {lfe: Linear Group Fixed Effecst},
author = {Simen Gaure},
year = {2013},
note = {R package version 1.4-963},
}