Splitting theorems for pro-$p$ groups acting on pro-$p$ trees and   2-generated subgroups of free pro-$p$ products with procyclic amalgamations
  Let G be a finitely generated infinite pro-p group acting on a pro-p tree such that the restriction of the action to some open subgroup is free. Then we prove that G splits as a pro-p amalgamated product or as a pro-p HNN-extension over an edge stabilizer.   Using this result we prove under certain conditions that free pro-p products with procyclic amalgamation inherit from its free factors the property of each 2-generated subgroup being free pro-p. This generalizes known pro-p results, as well as some pro-p analogs of classical results in abstract combinatorial group theory. 
Wolfgang Herfort, Pavel Zalesskii and Theo Zapata
math.GR