The main question to validate it by asking the users“  How would you feel if you could no longer use “the product”?”

https://review.firstround.com/how-superhuman-built-an-engine-to-find-product-market-fit/

Introducing the framework

https://www.lennysnewsletter.com/p/a-framework-for-finding-product-market

download this metric template : https://docs.google.com/spreadsheets/d/1SUK367AdZCMaR_iPeTDk8BJA2_MNwKM_PJSMUpuTDK8/edit?gid=0#gid=0

startup saatio stuff Product Market Fit