Anchor: I wondered how I could have been so unobservant as to overlook this. 
Entailed: I wondered how I overlooked this.
Contradiction: I didn't overlook a thing.
Contradiction: The Western and Eastern Empires fell at the same time.
Contradiction: The children were free from slavery.
Contradiction: Whittington rode his bike.
Contradiction: There is a dog on the beach.