How do I find a company's subsidiaries?
Your company's annual report (10-K). See: "Where can I get an annual report (10-K)?"
Look at a Company Profile in:
Other databases to try are listed on the Company Profiles & Directories area of the Company Research Guide or you can ask a Librarian for assistance with Lexis Corporate Affiliations [an 8 volume print set available at the Reference Desk].