@article{GDZPPN002477106,
title = {Idempotency of Circuit-induced Exchange Operators.},
journal = {Monatshefte f\"ur Mathematik},
volume = {74},
year = {1970},
pages = {330-335},
zbl = {0239.05130},
url = {http://dml.mathdoc.fr/item/GDZPPN002477106}
}
Sabidussi, Gert. Idempotency of Circuit-induced Exchange Operators.. Monatshefte für Mathematik, Tome 74 (1970) pp. 330-335. http://gdmltest.u-ga.fr/item/GDZPPN002477106/