Paper is related to Written. Written is related to Sign. 
Certain is related to Very. Very is related to Heavy. Heavy is related to Truck. Roof is part of Truck. 
Paper <--RelatedTo--> Written <--RelatedTo--> Sign 
Certain <--RelatedTo--> Very <--RelatedTo--> Heavy <--RelatedTo--> Truck <--PartOf-- Roof 