Nickel & Wilner (1984: 24) claim that “Relative clauses may be used to specify a human character (using di or dati), a non-human character (using di or san), a location (using pe), or a manner (using fa).” It seems, however, that either di or san may be used with both human and non-human referents.
Source: Wilner 1992: 19
Source: Winford 2000: 71
Source: Winford 2000: 111