Where to find Registry Numbers and physical property data for chemical substances?

1. Merck Index (in paper; an encyclopedia of chemicals, drugs, and biologicals; contains indexes arranged by Registry Number, molecular formula, chemical name, etc.)

CRC Handbook of Chemistry and Physics (in paper)

Dictionary of Organic Compounds (and supplements; in paper)

Dictionary of Inorganic Compounds (and supplements; in paper)

International Critical Tables of Numerical Data, Physics, Chemistry and Technology (online and available in paper)

Kirk-Othmer Encyclopedia of Chemical Technology (in paper; 3rd edition)

Kirk-Othmer Concise Encyclopedia of Chemical Technology (in paper; 4th edition)

Knovel Critical Tables (online)

Lange's Handbook of Chemistry (in paper)

Smithsonian Physical Tables (online and available in paper; 9th revised edition)

2. ChemFinder.Com (online; CambridgeSoft Corporation)

NIST Chemistry WebBook (online; U.S. National Institute of Standards and Technology)

Sigma-Aldrich (online)

3. CrossFire Beilstein (online; for organic compounds only)

4. Registry File (online; available through the Chemical Abstracts service which can be accessed via SciFinder Scholar or STN)