自唐宋以来，以茶易马、通商贸易的茶马古道成了维系农耕中华和游牧民族乃至外族关系的桥梁和纽带。
O B-Time I-Time I-Time I-Time O O B-Thing O B-Thing O O O O O O B-Location I-Location I-Location I-Location O O B-Thing I-Thing B-Organization I-Organization I-Organization I-Organization O B-Organization I-Organization I-Organization I-Organization O O B-Organization I-Organization O O O O O O O O O