Who is they?
Amazon offers a generous credit program for college books since they can be resold again to other buyers.

A:
college books

Who is they?
The Crusaders fought many unholy enemies since they were considered unholy by the priests.

A:
many unholy enemies

Who is they?
The Dallas Cowboys lost their lead to the Redskins because they started to perform very well in the second half.

A:
the Redskins