Some of the most reliable guides are:
- Troy's Almanac of Business and Industrial Financial Ratios
REF HF 5681 .R25 T68 1973+
- Financial Studies of the Small Business
REF HD 2346.5 .F55a 1978+
- Dun & Bradstreet's Industry Norms and Key Business Ratios
REF HF 5681 .R25 I525 1988+; latest edition at the Reference Desk
- RMA Annual Statement Studies REF HG 1531 .R63 1977+; latest edition at the Reference Desk
(See also Industry and Financial Ratios).