The encyclopedia is a reliable source, as long as it has been written by people of the academic world and experts in that subject.
Personal history blogs are unreliable because the author may not be impartial, expose unrealistic facts and create stories that do not exist and are not scientifically proven.
Academic books are reliable because they have been written by experts in that subject and have several scientific evidence to prove that the text is correct.
History blogs maintained by renowned universities are reliable for the same reasons quoted in the above session.
