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参考
Rock Paintings of Helan Mountains(賀蘭山岩画)
Helanshan Rock Art is representative of rock paintings in northern China, with rich and concentrated subject matter. As of December 2020, tens of thousands of petroglyphs have been discovered,[5] and they were created between 10,000 and 3,000 years ago.[6]
[5] "Ningxia "digitally" protects the rock paintings of Helan Mountain". Xinhua News Agency. 2021-01-02
[6] "Ningxia Helan Mountains: An Unforgettable Journey to the Secret World". Sina. 2009-09-05.