https://wenku.baidu.com/view/f6c3e14bb9d528ea80c77952.html
https://wenku.baidu.com/view/b7d898fcf424ccbff121dd36a32d7375a517c64a.html?rec_flag=default&sxts=1553068047747
回帖：赤平投影原理及讲解
https://wenku.baidu.com/view/f6c3e14bb9d528ea80c77952.html
https://wenku.baidu.com/view/b7d898fcf424ccbff121dd36a32d7375a517c64a.html?rec_flag=default&sxts=1553068047747
https://wenku.baidu.com/view/f6c3e14bb9d528ea80c77952.html
https://wenku.baidu.com/view/b7d898fcf424ccbff121dd36a32d7375a517c64a.html?rec_flag=default&sxts=1553068047747