@article{1178241033,
author = {Klingenberg, Wilhelm and Sasaki, Shigeo},
title = {On the tangent sphere bundle of a $2$-sphere},
journal = {Tohoku Math. J. (2)},
volume = {27},
number = {4},
year = {1975},
pages = { 49-56},
language = {en},
url = {http://dml.mathdoc.fr/item/1178241033}
}
Klingenberg, Wilhelm; Sasaki, Shigeo. On the tangent sphere bundle of a $2$-sphere. Tohoku Math. J. (2), Tome 27 (1975) no. 4, pp. 49-56. http://gdmltest.u-ga.fr/item/1178241033/