@article{MZ_1967__102_170863,
     author = {Fred Richman and Elbert A. Walker},
     title = {Cotorsion {Free,} an {Example} of {Relative} {Injectivity.}},
     journal = {Mathematische Zeitschrift},
     pages = {115--119},
     publisher = {mathdoc},
     volume = {102},
     year = {1967},
     zbl = {0178.02405},
     url = {http://geodesic.mathdoc.fr/item/MZ_1967__102_170863/}
}