Dear HoHun,
Data sources by the item in details are not introduced on the site.
We regard the site itself as an edited data base because it covers not only Japan but U.S.A, Germany, Britain, France and Italy widely as if a volume of a book.
For checking their reliability, please access to its homepage below
航空機エンジン一覧
Click the green box and you can jump to U.S.A's engine list.
I didn't use a translation tool to post here because, if used, you can't jump to the link. Language tool may cut the link.
Or you can contact with Editor directly as I may let you know his mail address.
Best regards,
Shinpachi
Japanese Piston Engines 
Linear Mode
