@article{10_1017_S0017089512000195,
     author = {BART{\L}OMIEJCZYK, PIOTR and NOWAK-PRZYGODZKI, PIOTR},
     title = {THE {HOMOTOPY} {TYPE} {OF} {THE} {SPACE} {OF} {GRADIENT} {VECTOR} {FIELDS} {ON} {THE} {TWO-DIMENSIONAL} {DISC}},
     journal = {Glasgow mathematical journal},
     pages = {619--626},
     year = {2012},
     volume = {54},
     number = {3},
     doi = {10.1017/S0017089512000195},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089512000195/}
}