Anchor: It is at the heart of many a difference of opinion between the PRC and the Service, the Service and mailers, mailers and the PRC, and between groups of mailers.
Entailed: The PRC and the Service have had differences of opinion.
Contradiction: The PRC and the Service have never had any differences of opinion.
Contradiction: Daniel was able to do it and was prepared to teach the computer. 
Contradiction: Discovery of ground strategies for qualitative research 
Contradiction: The woman is driving her car.
Contradiction: A group of people in the city.