Sa Lina, a regional inheritor of the intangible cultural heritage of Hua'er, a type of folk song, in the Ningxia Hui autonomous region. XINHUA YINCHUAN — Sa Lina, 38, has juggled a hectic schedule recently, performing Hua'er, a type of folk song popular in northwestern China, not only in her hometown in Ningxia Hui autonomous region but also in the …