@article{GDZPPN00222108X, title = {The Elements of K2 (...s).}, journal = {Manuscripta mathematica}, volume = {25}, year = {1978}, pages = {173-178}, zbl = {0374.13009}, url = {http://dml.mathdoc.fr/item/GDZPPN00222108X} }
Hurrelbrink, Jürgen. The Elements of K2 (...s).. Manuscripta mathematica, Tome 25 (1978) pp. 173-178. http://gdmltest.u-ga.fr/item/GDZPPN00222108X/