A Quick Primer for Old school Gaming (https://friendorfoe.com/d/Old School Primer.pdf , https://drive.google.com/file/d/1Ow5SB7OkWIC1opuZql4gIgzjcGMk84Z4/view )

Principia Apocrypha (https://lithyscaphe.blogspot.com/p/principia-apocrypha.html)

Oil Fantasy (https://oilfantasy.blogspot.com/p/manifesto-oil-fantasy.html)

Muster A Primer for War (https://www.drivethrurpg.com/en/product/413382/Muster)