Aquellas vs. aquéllas
Note: The unaccented form "aquellas" can function as a pronoun (like "aquéllas") if it can be unambiguously deduced as such from context.
Aquellas
-
those (feminine; far from speaker and listener)
Conozco a aquellas chicas. (I know those girls.)Ella simpatizó con aquellas desafortunadas personas. (She sympathized with those unfortunate people.)
Aquéllas
-
those ones (feminine; far from speaker and listener)
Casi compré una de aquéllas. (I almost bought one of those.)¿Llevan aquéllas faldas blancas? (Do those girls wear white skirts?)