I usually put it in spanish, but you really don´t need the spanish word, because this law is running on almost every modern country (as states in "OTHER COUNTRIES"
"La utilización de cualquier material mediático en este canal está protegida por la Clausula de Uso Justo, contenida en el Acta de los Derechos de Reproducción y Copia de 1976
*, la cual PERMITE LA REDIFUSIÓN DE MATERIALES PROTEGIDOS POR DERECHOS DE REPRODUCCIÓN CUANDO SON UTILIZADOS CON PROPÓSITO EDUCATIVO, DE ANÁLISIS O DE CRÍTICA Y COMENTARIO."
*spanish equivalent: says you can use copyrighted stuff for educative, analysis, criticism or comment purposes. It doesnt states anything about historical or parody uses, but in other countries is also allowed.
I really encourage you to find more about this specific law in your country. Most of this problems are solved just using these words as advice: think them like a spell, THEY REALLY WORK (along other words, like Habeas corpus, habeas data, etc).
I hope I wont have any problem with my sample libraries, thanks to the fair use guidelines