Left Conjunct Agreement
It is well known that Spanish, as many other languages (including English), displays Left Conjunct Agreement (LCA), that is, under certain circumstances, the verb agrees with the left member of a coordinated subject:
(1) Estaba César y su ejército en la orilla opuesta del río
LCA is more common in postverbal subjects, and when at least one of the conjuncts has low referentiality (in (1) for instance, César is a unique individual, but not su ejército “his army”). It cannot happen when both conjuncts have high referentiality:
(2) * Estaba César y Pompeyo en la orilla opuesta del río
It is less known, however, that this phenomenon is not limited to verb-subject agreement. Participles are also subject to LCA:
(3) Sabe varios idiomas, incluido el inglés y el francés
It is worth noticing that the Spanish prescriptive discourse usually condemns the LCA (in both cases).