Let be a simple algebraic group over an algebraically closed field , and be a simple algebraic group over an algebraically closed field . Let be an isomorphism of groups between and (viz, only an isomorphism of the pure group structure). Then can be decomposed into a transfer of structures induced by an isomorphism between and , followed by a quasi-rational function relative to .
- Homomorphismes abstraites de groupes algebriques simples by Armand Borel and J Tits, Ann. Math 97 (1973), 499-571