This document summarizes a research paper on sentiment analysis and opinion mining. It discusses different levels of sentiment analysis including document, sentence and phrase level analysis. It also covers challenges in sentiment analysis such as named entity extraction, information extraction, sentiment determination, co-reference resolution and relation extraction. Finally, it reviews several approaches to sentiment analysis including using machine learning classifiers at sentence level and extracting associations between product features and opinions. The overall goal of the paper is to provide a literature survey of sentiment analysis and opinion mining techniques.