@article{01973827, title = {Harmonic }, journal = {Beitr\"age zur Algebra und Geometrie}, volume = {44}, year = {2003}, pages = {309-321}, zbl = {1045.53044}, language = {en}, url = {http://dml.mathdoc.fr/item/01973827} }
Bejan, C. L.; Benyounes, M. Harmonic . Beiträge zur Algebra und Geometrie, Tome 44 (2003) pp. 309-321. http://gdmltest.u-ga.fr/item/01973827/