Chain homotopy pullbacks and pushouts
Cahiers de Topologie et Géométrie Différentielle Catégoriques, Volume 23 (1982) no. 3, p. 269-278 
@article{CTGDC_1982__23_3_269_0,
     author = {Wong, Y. L.},
     title = {Chain homotopy pullbacks and pushouts},
     journal = {Cahiers de Topologie et G\'eom\'etrie Diff\'erentielle Cat\'egoriques},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {23},
     number = {3},
     year = {1982},
     pages = {269-278},
     zbl = {0503.55014},
     mrnumber = {675338},
     language = {en},
     url = {http://www.numdam.org/item/CTGDC_1982__23_3_269_0}
}

Wong, Y. L. Chain homotopy pullbacks and pushouts. Cahiers de Topologie et Géométrie Différentielle Catégoriques, Volume 23 (1982) no. 3, pp. 269-278. http://www.numdam.org/item/CTGDC_1982__23_3_269_0/

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