The doctors' steles are a valuable historical resource for the study of culture, education and sculpture in Vietnam. 82 stelae remain. They depict the names and birth places of 1307 graduates of 82 triennial royal exams. Between 1442 and 1779, eighty-one exams were held by the Lê dynasty and one was held by the Mạc dynasty. The ancient Chinese engravings on each stele praise the merits of the monarch and cite the reason for holding royal exams. They also record the mandarins who were tasked with organising the exams. It used to be common to rub the stone turtles' heads, but now there is a fence that is meant to prevent people from doing this in order to preserve the turtles.