@article{700816,
     title = {Symmetric approach to the fundamental notions of general topology},
     booktitle = {General Topology and its Relations to Modern Analysis and Algebra},
     series = {GDML\_Books},
     publisher = {Academia Publishing House of the Czechoslovak Academy of Sciences},
     address = {Praha},
     year = {1967},
     pages = {308-319},
     mrnumber = {MR0232333},
     zbl = {0168.43403},
     url = {http://dml.mathdoc.fr/item/700816}
}

Schmidt, J. Symmetric approach to the fundamental notions of general topology, dans General Topology and its Relations to Modern Analysis and Algebra, GDML_Books,  (1967), pp. 308-319. http://gdmltest.u-ga.fr/item/700816/