Yabla video uses of 考证

无从 wúcóng
考证 kǎozhèng
zhè
shì
千年前 qiānniánqián
还是 háishì
两千年 liǎngqiānnián
qián
de
shì
With no historical record, it was something that [we believe] happened 1,000 to 2,000 years ago.