My research topic is \”Characterization of sham-chewing behavior and the development a valid measurement of sham-chewing in group housed sows\”. I would upload my proposal later. I need the literature review part include: 1. Review of stereotypical behavior and stereotypical behavior in pigs; 2. Review of sham chewing behavior in pigs: a) what has been examined; b) what we know; c) what sampling method others used? 3. Review of behavior assessment method and sampling method: reliability test and stereotypical behavior sampling. Please spend more words on the review of sow sham chewing. Try not to use the web resources. The resources should from books, articles and journals.