@article{1077469293, author = {Isbell, J. R.}, title = {Natural sums and direct decompositions}, journal = {Duke Math. J.}, volume = {27}, number = {1}, year = {1960}, pages = { 507-512}, language = {en}, url = {http://dml.mathdoc.fr/item/1077469293} }
Isbell, J. R. Natural sums and direct decompositions. Duke Math. J., Tome 27 (1960) no. 1, pp. 507-512. http://gdmltest.u-ga.fr/item/1077469293/