https://science.howstuffworks.com/innovation/inventions/10-ancient-chinese-inventions.htm
https://www.ancient-origins.net/unexplained-phenomena/dropa-stones-00877
https://www.discoveryuk.com/mysteries/mysteries-of-the-east-the-intriguing-legend-of-the-dropa-stones/
https://www.crystalinks.com/dropa.html
https://www.iflscience.com/dropa-stones-elaborate-hoax-or-alien-artifact-70048
http://www.ancient-wisdom.com/chinadropa.htm
https://www.science20.com/archyfantasies/10_most_notsopuzzling_ancient_artifacts_2_dropa_stones-91343
https://www.reddit.com/r/fascinating/comments/xlk5od/the_dropa_stones_were_stone_discs_with/
https://www.quora.com/Is-there-any-truth-behind-the-story-of-Chinese-Dropa-stones
https://www.youtube.com/watch?v=d20Pl0lby7U
https://www.globalonenessproject.org/library/photo-essays/drokpa-nomadic-mountain-people-tibet
http://www.badarchaeology.com/out-of-place-artefacts/mysterious-objects/the-dropa-or-dzopa-stones/