@article{MZ_1973__130_171863,
     author = {Philip R. Heath},
     title = {Groupoid {Operations} and {Fibre-Homotopy} {Equivalence.} {I.}},
     journal = {Mathematische Zeitschrift},
     pages = {207--234},
     publisher = {mathdoc},
     volume = {130},
     year = {1973},
     zbl = {0253.55008},
     url = {http://geodesic.mathdoc.fr/item/MZ_1973__130_171863/}
}