@article{CMH_1953__27_139067,
     author = {R. Bott and H. Samelson},
     title = {On the {Pontryagin} product in spaces of paths.},
     journal = {Commentarii mathematici Helvetici},
     pages = {320--337},
     year = {1953},
     volume = {27},
     zbl = {0052.19301},
     url = {http://geodesic.mathdoc.fr/item/CMH_1953__27_139067/}
}