The Dynkin and the extended Dynkin graphs are characterized by representations over the real numbers.
@article{bwmeta1.element.bwnjournal-article-cmv81i2p293bwm, author = {Lidia H\"ugeli and Sverre Smal\o }, title = {Real representations of quivers}, journal = {Colloquium Mathematicae}, volume = {79}, year = {1999}, pages = {293-297}, zbl = {0953.16013}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-cmv81i2p293bwm} }
Hügeli, Lidia; Smalø, Sverre. Real representations of quivers. Colloquium Mathematicae, Tome 79 (1999) pp. 293-297. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-cmv81i2p293bwm/
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