Assistant is related to Servant. Servant is related to Little. Little is related to Quantity. Volume is a type of Quantity. 
Literature is related to Subject. Subject is related to Culture. Culture is related to Ethnic. 
Assistant <--RelatedTo--> Servant <--RelatedTo--> Little <--RelatedTo--> Quantity <--IsA-- Volume 
Literature <--RelatedTo--> Subject <--RelatedTo--> Culture <--RelatedTo--> Ethnic 