THE BIG QUESTION
When markets unable to satisfy important economic objectives does government intervention help?
Positive and Negative Externalities
Positive and Negative Externalities Further Study Resources
PDF Resources from Brad Cartwright (an online economic tutor): Note - These resources refers to video resources we don't have access to, however, I think the documents are very good summaries of each of the externalities (with diagrams and examples) and useful for your revision and study.
Environmental Economics