The bible is Vic Flintham, Air Wars & Aircraft, Arms&Armour,1989:
P.98: (Port)Guinea(Bissau): 23/3/1973: 2 FAP G.91 (R-4, Esq.121) “were shot down by (PAIGC guerillas’) SA-7s and a third (was) lost 6 weeks later”. P.115: Esq.93, Angola; P.117 “a G.91 was claimed as shot down” (24/11/1975). P.121 Esq.502, 702, Mozambique: no losses noted.