Simplify the following text for a Grade 13 native English-speaking person.
Original: Some historical accounts suggest that many sub tribes ( including the Cheemas ) of the Jatts were `` oppressed '' by Hindu king Raja Dahir who ruled over Punjab where the majority of the population followed Buddhism ( Ram Swarup Joon : History of the Jats , Rohtak , India ( 1938 , 1967 ) ) .
Simplified: Many Jatt\/Cheema were oppressed by Hindu king Raja Dahir who ruled over Punjab where the majority of the population followed Buddhism ( Ram Swarup Joon : History of the Jats , Rohtak , India ( 1938 , 1967 ) ) .