are not obliged to prepare their consolidated financial statements in accordance with IFRS (International Financial Reporting Standards)

Les sociétés qui sont listées à la bourse sont tenues à établir leurs comptes consolidés d'après IFRS (anciennement IAS - International Accounting Standards).

Consolidated financial statements
The ultimate parent company of a group must produce consolidated financial statements including all of its subsidiaries (IAS27.9). A subsidiary is an entity which is controlled by another entity; control is the power to govern the financial and operating policies (IAS27.4). In preparing consolidated financial statements, balances, transactions, income and expenses with other group members are eliminated
http://en.wikipedia.org/wiki/International_Financial_Reporti... Financial Reporting Standards (IFRS)

A set of international accounting standards stating how particular types of transactions and other events should be reported in financial statements. IFRS are issued by the International Accounting Standards Board.

IFRS are sometimes confused with International Accounting Standards (IAS), which are the older standards that IFRS replaced. (IAS were issued from 1973 to 2000.)

The goal with IFRS is to make international comparisons as easy as possible. This is difficult because, to a large extent, each country has its own set of rules. For example, U.S. GAAP are different from Canadian GAAP. Synchronizing accounting standards across the globe is an ongoing process in the international accounting community.
http://www.investopedia.com/terms/i/ifrs.asp