Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: good reference

this book can be a good reference source for those learning portuguese. it's a small, dense book composed purely of grammar rules. you'll definitely need other sources to supplement this one. i used this book while i was in brazil learning portuguese and it was very helpful in clarifying any grammar doubts i had.each small grammar section includes some examples to help give some context.this is a far from comprehensive resource for studying portuguese but can be a helpful part of the armament.