Exhibit 3.22

CERTIFICATE OF LIMITED PARTNERSHIP

OF

CDP INVESTORS, L.P.

This Certificate (the “Certificate) of Limited Partnership of CDP Investors, L.P., a Delaware limited partnership (the ‘Partnership”), is being executed on May 8, 1997.

It is, therefore, certified as follows:

1.Name.  The name of the Partnership is:

CDP Investors, L.P.

2.Registered Office and Registered Agent.  The registered office of the Partnership in the State of Delaware is located at 1013 Centre Road, Wilmington, New Castle County, Delaware 19805-1297.  The name of the registered agent of the Partnership for Service of Process at such address is The Prentice-Hall Corporation System, Inc.

3.Name and Address of General Partner.  The name and address of the General Partner of the Partnership is as follows:

CDP GP, Inc.

200 West Madison Street

38th Floor

Chicago, Illinois 80808

4.Certificate.  This Certificate has been duly executed and filed in accordance with the provisions of Section 17-201 of the Delaware Revised Uniform Limited Partnership Act.

IN WITNESS WHEREOF, the undersigned has duly executed this Certificate as of the day and year first above written.

CDP GP, Inc., a Delaware corporation
By:	/s/ Glen Miller
	Its:	VP

CERTIFICATE OF AMENDMENT

TO

CERTIFICATE OF LIMITED PARTNERSHIP

OF

CDP INVESTORS, L.P.

It is hereby certified that:

FIRST: The name of the limited partnership (hereinafter called the “partnership”) is

CDP INVESTORS, L.P.

SECOND: Pursuant to provisions of Section 17-202, Title 6, Delaware Code, the Certificate of Limited Partnership is amended as follows:

“3.Name and Address of General Partner.  The name and address of the General Partner of the Partnership is as follows:

CDP GP, Inc.

200 West Madison Street

Suite 2500

Chicago, Illinois 60606

The undersigned, a general partner of the partnership, executed this Certificate of Amendment on the 13th day of June, 2000.

CDP GP, INC., a Delaware corporation, the general partner
By:	/s/ Glen Miller
	Glen Miller
Its:	Vice President

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CERTIFICATE OF AMENDMENT

TO

CERTIFICATE OF LIMITED PARTNERSHIP

OF

CDP INVESTORS, L.P.

It is hereby certified that:

FIRST:The name of the limited partnership (hereinafter called the “Partnership”) is

CDP INVESTORS, L.P.

SECOND:Pursuant to provisions of Section 17-202, Title 6, Delaware Code, the Certificate of Limited Partnership is amended as follows:

“3.Name and Address of General Partner.  The name and address of the General Partner of the Partnership is as follows:

CDP GP, INC.

71 South Wacker Drive, 12th Floor

Chicago, Illinois 60606

The undersigned, a general partner of the Partnership, executed this Certificate of Amendment on the 1st day of March, 2005.

CDP GP, INC.
By:	/s/ Kirk Rose
	Kirk Rose
	Vice President, Treasurer

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