Trouble is a synonym of Difficulty. Difficulty is a synonym of Obstacle. Obstacle is related to Hazard. 
Note is related to Material. Material is related to Report. Report is related to Condition. Condition is related to Poverty. 
Trouble <--Synonym--> Difficulty <--Synonym--> Obstacle <--RelatedTo--> Hazard 
Note <--RelatedTo--> Material <--RelatedTo--> Report <--RelatedTo--> Condition <--RelatedTo--> Poverty 