Copper Mountains
The Copper Mountains lie east of Yuma , Arizona and east of the Yuma Desert; also east of the Gila and Tinajas Altas Mountains . 
<triplet> Gila <subj> Copper Mountains <obj> has boundary <subj> Tinajas Altas Mountains <obj> has boundary <triplet> Tinajas Altas Mountains <subj> Yuma Desert <obj> has boundary <subj> Gila <obj> has boundary