Own mineral rights and need help finding out what companies are involved in issuing checks

Hi, I have recently acquired oil royalty interest in many different tracts in Upshur, Marion, Upshaw County including surveys of Lumbrera, Ferguson, and Hooper. I have the royalty interest, survey, operator and acres but this information is from 1976 when it was acquired by my father from his Aunt back in 1976. My father passed 13 years ago and gave my mom usufruct of the monies. She recently passed and I do not have access to her financial information, unfortunately. How do I go about finding out what companies hold the leases, what companies are paying the royalties?

Any help is greatly appreciated if you can guide me in the direction I need to go.

Thanks