Some Romance languages use two auxiliaries, to have and to be for compound tenses, as ho caminato (Italian), j'ai marché (French) , but sono andato, je suis allé. There are few verbs requiring the auxiliary to be, but they are very common. Instead Romanian, Catalan, Spanish, Portuguese use just one auxiliary. I've also read that some intransitive verbs were conjugated in old Spanish with ser, as in Buen, don Guido, ya eres ido y para siempre jamás. I wonder if texts of old Spanish and other Romance languages show this feature and, if so, from what period the auxiliary a avea, haber ... has prevailed. Thanks to all of you.