Frey 1986. Frey, Gerhard (1986), "Links between stable elliptic curves and certain Diophantine equations", Annales Universitatis Saraviensis. Series Mathematicae, 1 (1): iv+40, ISSN0933-8268, MR0853387
A synthetic presentation (in French) of the main ideas can be found in thisBourbaki article of Jean-Pierre Serre. For more details see Hellegouarch 2001
Frey 1986. Frey, Gerhard (1986), "Links between stable elliptic curves and certain Diophantine equations", Annales Universitatis Saraviensis. Series Mathematicae, 1 (1): iv+40, ISSN0933-8268, MR0853387