Topological complexity of the relative closure of a semi-Pfaffian couple
  Gabrielov introduced the notion of relative closure of a Pfaffian couple as an alternative construction of the o-minimal structure generated by Khovanskii's Pfaffian functions. In this paper, use the notion of format (or complexity) of a Pfaffian couple to derive explicit upper-bounds for the homology of its relative closure.   Keywords: Pfaffian functions, fewnomials, o-minimal structures, Betti numbers. 
Thierry Zell