@article{MM2_1969__1_153970,
     author = {Hans-Berndt Brinkmann},
     title = {Baer {Addition} of {Extensions.}},
     journal = {Manuscripta mathematica},
     pages = {99--110},
     publisher = {mathdoc},
     volume = {1},
     year = {1969},
     zbl = {0164.01303},
     url = {http://geodesic.mathdoc.fr/item/MM2_1969__1_153970/}
}