@incollection{AST_1979__63__73_0,
     author = {Hazewinkel, Michiel},
     title = {On formal groups. {The} functional equation lemma and some of its applications},
     booktitle = {Journ\'ees de G\'eom\'etrie Alg\'ebrique de Rennes - (Juillet 1978) (I) : Groupe formels, repr\'esentations galoisiennes et cohomologie des vari\'et\'es de caract\'eristique positive},
     series = {Ast\'erisque},
     pages = {73--82},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {63},
     year = {1979},
     mrnumber = {563461},
     zbl = {0423.14028},
     language = {en},
     url = {http://archive.numdam.org/item/AST_1979__63__73_0/}
}