@article{GDZPPN002061198, title = {The Signature Defect and the Homotopy of BPL and PL/O}, journal = {Commentarii mathematici Helvetici}, volume = {48}, year = {1973}, pages = {525-530}, zbl = {0279.57012}, url = {http://dml.mathdoc.fr/item/GDZPPN002061198} }
Frank, David. The Signature Defect and the Homotopy of BPL and PL/O. Commentarii mathematici Helvetici, Tome 48 (1973) pp. 525-530. http://gdmltest.u-ga.fr/item/GDZPPN002061198/