Determine which secondary sources are reliable and which are unreliable

encyclopedias

personal history blogs

history blogs maintained by renowned universities

academic textbooks

Encyclopedias are reliable

Personal history blogs are not reliable

History blogs are reliable

Academic Textbooks are reliable

The answers to your question is,

Encyclopedias are reliable, since they practically have anything you are looking for, unless you are talking about online encyclopedias, then those aren't that trustworthy. They can be changed easily.

Personal history blogs are not reliable, as they can be fictional history made by the creator. It could possibly contain anything.

History blogs maintained by renowned universities are reliable, assuming that they are a very educated university. There are possibilities for fake information or wrong information, though.

Academic Textbooks are reliable, they were made to be used as a resource for studying and all. People rely on information from the ones who make these books.

-Mabel <3