1. Extending Pollard’s theorem for t-representable sums;Grynkiewicz;Israel J. Math.,2010
2. Y.O. Hamidoune, O. Serra, A note on Pollard’s Theorem, 2008, p. 7. http://arxiv.org/abs/0804.2593.
3. On intersections of finitely generated subgroups of free groups;Neumann;Publ. Math. Debrecen,1956
4. On intersections of finitely generated subgroups of free groups;Neumann;Publ. Math. Debrecen,1957
5. Joel Friedman, Sheaves on graphs, their homological invariants, and a proof of the Hanna Neumann conjecture: with an appendix by Warren Dicks Memoirs, AMS (in press).