| Bibliographies and reviews | |||||
| Grading | Nationality | Population registers | Race | Minorities | Suicide |
| A | An excellent source with few serious problems |
| B | A good source with some serious problems |
| C | A fair source with quite a few serious problems |
| D | A poor source with too many serious problems |
| E | Best read with an eye for studying how not to write |
| U | Ungraded as a work described only for reference |