The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the reporting entity. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, but excludes any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.
Companies should report their financial performance in their annual financial reports, and these are the best places to find this information.
For companies that file with the SEC, this information can be found within their "Form 10-K" filings. You can often find these documents by searching for "Company 10-k", or they can be found through the SEC's EDGAR search.