@article{MM2_1987__58_155228,
     author = {R.W. Kieboom},
     title = {A {Pullback} theorem for cofibrations.},
     journal = {Manuscripta mathematica},
     pages = {381--384},
     publisher = {mathdoc},
     volume = {58},
     year = {1987},
     zbl = {0617.55002},
     url = {http://geodesic.mathdoc.fr/item/MM2_1987__58_155228/}
}