Advertising supplements periodically accompany corresponding newspapers and are prepared by the paper's advertising staff instead of its editorial staff. It is common for them to cover topics such as real estate and automobiles on behalf of the paper's frequent advertisers. Some supplements are spin-offs from a newspaper. They are sold separately and typically cover a specific topic, such as the Times Literary Supplement and the Times Educational Supplement Supplements found on some DVDs, HD DVDs, and Blu-rays are more commonly known as special features, bonus features, or bonus material.