Your search returned the following 2 documents:

2. $\forall\exists^\ast$-Equational Theory of Context Unification is $\Pi_1^0$-Hard
   Sergei Vorobyov
   In: Proceedings of the 23rd International Symposium on Mathematical Foundations of Computer Science (MFCS-98), Brno, Czech Republic, August 1998, 1998, 597-606
   [PS: Download: paper80.ps]
   
1. On Name Generation and Set-Based Analysis in the Dolev-Yao Model
   Witold Charatonik and Roberto Amadio
   In: CONCUR 2002 - Concurrency Theory. 13th International Conference, Brno, Czech Republic, 2002, 499-514