Expression is a type of Agent. Agent is related to Investigator. 
Understand requires Think. Read is a type of Understand. Read is a type of Have. Sustain is a type of Have. 
Expression --IsA--> Agent <--RelatedTo--> Investigator 
Think <--HasPrerequisite-- Understand <--IsA-- Read --IsA--> Have <--IsA-- Sustain 