CAUTION: The Sender of this email is not from within Dalhousie. This is implicit in Ch. 2 of @book{0004.36904, author="Reidemeister, Kurt", title="{Einf\"uhrung in die kombinatorische Topologie.}", language="German", publisher="{Braunschweig: Friedr. Vieweg \& Sohn A.-G. XII, 209 S. }", year="1932", keywords="{topology}", } Every group is a homomorphic image of a free group. Presumably it also implicit in @Article{zbMATH02581122, Author = {O. {Schreier}}, Title = {{Die Untergruppen der freien Gruppen.}}, FJournal = {{Abhandlungen aus dem Mathematischen Seminar der Universit\"at Hamburg}}, Journal = {{Abh. Math. Semin. Univ. Hamb.}}, ISSN = {0025-5858; 1865-8784/e}, Volume = {5}, Pages = {161--183}, Year = {1927}, Publisher = {Springer, Berlin/Heidelberg}, Language = {German}, Zbl = {53.0110.01} } Johannes HUEBSCHMANN Johannes Professeur émérite Université de Lille - Sciences et Technologies Département de Mathématiques CNRS-UMR 8524 Laboratoire Paul Painlevé Labex CEMPI (ANR-11-LABX-0007-01) 59 655 VILLENEUVE D'ASCQ Cedex/France http://math.univ-lille1.fr/~huebschm Johannes.Huebschmann@univ-lille.fr ----- Mail original ----- De: "porst" <porst@uni-bremen.de> À: "categories@mta.ca list" <categories@mta.ca> Envoyé: Mardi 14 Juillet 2020 18:08:51 Objet: categories: Looking for a reference Dear all, If I am not mistaken the characterization of free groups by its universal property has first been shown in the late 1920s. Does anybody know a reference? Hans-E. Porst -- Hans-E. Porst porst@uni-bremen.de <mailto:porst@uni-bremen.de> [For admin and other information see: http://www.mta.ca/~cat-dist/ ]