@article{GDZPPN00205888X,
title = {The Index of a Tangent 2-Field.},
journal = {Commentarii mathematici Helvetici},
volume = {42},
year = {1967},
pages = {86-110},
zbl = {0153.53504},
url = {http://dml.mathdoc.fr/item/GDZPPN00205888X}
}
Thomas, Emery. The Index of a Tangent 2-Field.. Commentarii mathematici Helvetici, Tome 42 (1967) pp. 86-110. http://gdmltest.u-ga.fr/item/GDZPPN00205888X/