Source is a synonym of Beginning. Beginning is related to Morning. Morning is related to Sleep. Sleep can be Useful. 
Invisible is related to Hear. Hear is related to Vision. Vision is a synonym of Desire. 
Source <--Synonym--> Beginning <--RelatedTo--> Morning <--RelatedTo--> Sleep --HasProperty--> Useful 
Invisible <--RelatedTo--> Hear <--RelatedTo--> Vision <--Synonym--> Desire 