The Chinese state-controlled company that acquired Calgary-based Nexen in a landmark $15.1-billion takeover, CNOOC Ltd., begins trading on Canada's largest stock market today.

The share-substitutes, known as American depository receipts or ADRs, will have the symbol CNU on the Toronto Stock Exchange.

No new equity is being issued but the listing but gives Canadians insight into CNOOC's market value.

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The TSX listing was part of CNOOC's commitments to win approval for the takeover from the Canadian government.

The Harper government approved the CNOOC-Nexen deal in December under existing foreign-takeover rules but also announced that future deals by state-owned enterprises would face greater scrutiny.