Why are tertiary sources, such as websites and magazines, usually considered less dependable than primary or secondary sources of scientific information? o o tertiary sources have not been fact-checked by reviewers, so the information in tertiary sources is never reliable. tertiary sources provide information based solely on opinion, rather than scientific fact tertiary sources are not usually authored by scientists and therefore do not provide reliable information tertiary sources usually do not cite information from primary sources, and may perpetuate errors made by secondary sources