@article{GDZPPN002351536, title = {Boundaries for Natural Systems II.}, journal = {Mathematica Scandinavica}, volume = {30}, year = {1972}, pages = {281-289}, zbl = {0245.46079}, url = {http://dml.mathdoc.fr/item/GDZPPN002351536} }
Brooks, R.M. Boundaries for Natural Systems II.. Mathematica Scandinavica, Tome 30 (1972) pp. 281-289. http://gdmltest.u-ga.fr/item/GDZPPN002351536/