Free Steiner triple systems and their automorphism groups
  The paper is devoted to the study of free objects in the variety of Steiner loops and of the combinatorial structures behind them, focusing on their automorphism groups. We prove that all automorphisms are tame and the automorphism group is not finitely generated if the loop is more than $3$-generated. For the free Steiner loop with $3$ generators we describe the generator elements of the automorphism group and some relations between them. 
A. Grishkov, D. Rasskazova, M. Rasskazova, I. Stuhl
math.GR