SEATTLE (AP) — Amazon.com is introducing a referral service to help people to get projects and chores done around their homes. The recommendation system, called Amazon Home Services, marks the e-commerce company's latest attempt to expand its empire beyond online shopping. Amazon.com's move poses a potential threat to other online referral and business rating services, including Angie's List, Yelp and Thumbtack, a startup whose backers include Google. About 700 different services in major U.S.