@article{CM_1936__3__391_0,
     author = {Baer, Reinhold and Levi, Friedrich},
     title = {Freie {Produkte} und ihre {Untergruppen}},
     journal = {Compositio Mathematica},
     pages = {391--398},
     publisher = {Johnson Reprint Corporation},
     volume = {3},
     year = {1936},
     zbl = {0015.00601},
     language = {de},
     url = {http://www.numdam.org/item/CM_1936__3__391_0/}
}