Ref.
https://archive.org/details/buddhismprimitiv00copeuoft
https://archive.org/details/buddhismprimiti01coplgoog

ดาวน์โหลดไฟล์ pdf
https://ia802701.us.archive.org/23/items/buddhismprimitiv00copeuoft/buddhismprimitiv00copeuoft.pdf

https://archive.org/download/buddhismprimiti01coplgoog/buddhismprimiti01coplgoog.pdf