Chapter IX sets up quite a good system of guarantees, including representatives of parties and blocs in the election commissions (again too long and reiterative articles: see, e.g., Article 44.3 and 44.6, 44.4 and 44.7). Concerning guarantees for candidates, and official observers, i.e. partisans and from international organisations, there is no place for national, non-partisan observers; but in the general context of guarantees, it does not seem to be excessively important.
