Up until 1991 CMLL operated Being_in_operation under the name Name_conferral Empresa Mexicana de Lucha Libre ( EMLL ) or some times as NWA-EMLL , to promote Cause_change_of_position_on_a_scale their association Collaboration with the National Wrestling Alliance ( NWA ) that ended Process_end in 1991 and prompted Cause_change_of_position_on_a_scale the name change Change .