In ancient China, geographical literature dates to the 5th century BCE. The oldest extant Chinese maps come from the State of Qin, dated back to the 4th century BCE, during the Warring States period. In the book of the "Xin Yi Xiang Fa Yao", published in 1092 by the Chinese scientist Su Song, a star map on the equidistant cylindrical projection. Although this method of charting seems to have existed in China even before this publication and scientist, the greatest significance of the star maps by Su Song is that they represent the oldest existent star maps in printed form.