Concentration is a type of Attention. Focus is a type of Concentration. Focus is related to Lens. 
Bible is related to Cross. Cross is related to Related. Related is related to Eat. 
Attention <--IsA-- Concentration <--IsA-- Focus <--RelatedTo--> Lens 
Bible <--RelatedTo--> Cross <--RelatedTo--> Related <--RelatedTo--> Eat 