Physics, Astrophysics and Astronomy Literature is Historically Classified into Two Types
1. Primary Sources
ArXiv.org
Journals of Periodicals
Technical Reports - Government or Industry
Patents - U.S. or Foreign
Dissertations
2. Secondary Sources
Periodicals (Reviews) - Physical Review Letters, Applied Physics Letters
Abstracting and Indexing Sources - Compendex, Academic Search Premier, Google Scholar
Handbooks, Dictionaries - Handbook of Chemistry and Physics, Dictionary of Physics
Encyclopedias - Encyclopedia of Applied Physics, Encyclopedia of Physics
Data Collections - Norton's Star Atlas and Reference Handbook
Treatised and Monographs - Annual Review of Astronomy and Astrophysics
Textbooks