ADRs are the equivalent of shares in non-U.S. companies that trade in the U.S. You can find information about ADRs in American Depositary Receipts: Selected Materials 1955-1973, Loss & Seligman's Securities Regulation (Aspen), Proxy Statements Strategy and Forms (Jefren Publishing), Allan Afterman's U.S. Securities Regulation of Foreign Issuers / Financial Reporting and Disclosure Manual and Rosenblum's Investment Company Determination Under the 1940 Act (Aspen).
J P Morgan has a Web page that provides information about ADRs (www.adr.com). The page provides quotes, information on industry sectors, analyst estimates, etc.
For more information, search PLI handbooks, legal news databases and/or law reviews on Lexis and Westlaw.