When a bibliography is built by extracting references from a data base — as BibTeX does when it builds a bibliography for a LaTeX document — these references are usually sorted w.r.t. author names. Nevertheless, most of implementations of lexical order relations on person names consist of concatenations of the parts of name: first name, particle, last name. We show that this may lead to incorrect results in some particular cases (some examples are given using BibTeX). Then we explain how this problem is solved in MlBibTeX, our multilingual reimplementation of BibTeX.