Substantial is a synonym of Wealthy. Wealthy is related to Rich. 
Introduction is related to Beginning. Beginning is related to Story. you are likely to find Story in/at/on Past. Past is a type of History. 
Substantial <--Synonym--> Wealthy <--RelatedTo--> Rich 
Introduction <--RelatedTo--> Beginning <--RelatedTo--> Story --AtLocation--> Past --IsA--> History 