EX-4.1



 EXHIBIT 4.1 
 CUSIP No. 003687209 
 AGREEMENT CONCERNING JOINT FILING OF SCHEDULE 13D 

The undersigned agree as follows: 
 (i) each of them is individually eligible to use Schedule 13D to which this Exhibit is attached, and such Schedule 13D is filed on behalf of each of them; and 

(ii) each of them is responsible for the timely filing of such Schedule 13D and any amendments thereto, and for the completeness and
accuracy of the information concerning such person contained therein; but none of them is responsible for the completeness or accuracy of the information concerning the other person making the filing, unless such person knows or has reason to
believe that such information is inaccurate. 
 This Agreement may be executed in any number of counterparts, each of which
shall be deemed to be an original, but all of which, taken together, shall constitute one and the same instrument. 
 Dated as
of December 6, 2011 

  
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	V. PREM WATSA
	
	/s/ V. Prem Watsa
	
	1109519 ONTARIO LIMITED
		
	By:	 	/s/ V. Prem Watsa
		 	Name:	 	V. Prem Watsa
		 	Title:	 	President
	
	THE SIXTY TWO INVESTMENT COMPANY LIMITED
		
	By:	 	/s/ V. Prem Watsa
		 	Name:	 	V. Prem Watsa
		 	Title:	 	President
	
	810679 ONTARIO LIMITED
		
	By:	 	/s/ V. Prem Watsa
		 	Name:	 	V. Prem Watsa
		 	Title:	 	President
	
	FAIRFAX FINANCIAL HOLDINGS LIMITED
		
	By:	 	/s/ V. Prem Watsa
		 	Name:	 	V. Prem Watsa
		 	Title:	 	Chairman and Chief Executive Officer



  
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	TIG INSURANCE COMPANY
		
	By:	 	/s/ John. J. Bator
		 	Name:	 	John J. Bator
		 	Title:	 	Chief Financial Officer and Senior Vice President
	
	FAIRMONT SPECIALTY INSURANCE COMPANY
		
	By:	 	/s/ John. J. Bator
		 	Name:	 	John J. Bator
		 	Title:	 	Chief Financial Officer and Senior Vice President
	
	GENERAL FIDELITY INSURANCE COMPANY
		
	By:	 	/s/ John. J. Bator
		 	Name:	 	John J. Bator
		 	Title:	 	Chief Financial Officer and Senior Vice President



  
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	THE NORTH RIVER INSURANCE COMPANY
		
	By:	 	/s/ Paul Bassaline
		 	Name:	 	Paul Bassaline
		 	Title:	 	Vice President & Controller
	
	UNITED STATES FIRE INSURANCE COMPANY
		
	By:	 	/s/ Paul Bassaline
		 	Name:	 	Paul Bassaline 
		 	Title:	 	Vice President & Controller



  
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	ODYSSEY REINSURANCE COMPANY
		
	By:	 	/s/ Kirk M. Reische
		 	Name:	 	Kirk M. Reische
		 	Title:	 	Vice President
	
	CLEARWATER INSURANCE COMPANY
		
	By:	 	/s/ Kirk M. Reische
		 	Name:	 	Kirk M. Reische
		 	Title:	 	Vice President



  
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	MARKEL INSURANCE COMPANY OF CANADA
		
	By:	 	/s/ Craig Pinnock
		 	Name:	 	Craig Pinnock
		 	Title:	 	Director
	
	COMMONWEALTH INSURANCE COMPANY
		
	By:	 	/s/ Craig Pinnock
		 	Name:	 	Craig Pinnock
		 	Title:	 	Director
	
	FEDERATED INSURANCE COMPANY OF CANADA
		
	By:	 	/s/ Craig Pinnock
		 	Name:	 	Craig Pinnock
		 	Title:	 	Director
	
	LOMBARD GENERAL INSURANCE COMPANY OF CANADA
		
	By:	 	/s/ Craig Pinnock
		 	Name:	 	Craig Pinnock
		 	Title:	 	Director
	
	LOMBARD INSURANCE COMPANY
		
	By:	 	/s/ Craig Pinnock
		 	Name:	 	Craig Pinnock
		 	Title:	 	Director



  
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	ZENITH INSURANCE COMPANY
		
	By:	 	/s/ Michael Jansen
		 	Name:	 	Michael Jansen
		 	Title:	 	Executive Vice President and General Counsel



  
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	SENECA INSURANCE COMPANY, INC.
		
	By:	 	/s/ James V. Kraus
		 	Name:	 	James V. Kraus
		 	Title:	 	Assistant Vice President



  
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	FAIRFAX (BARBADOS) INTERNATIONAL CORP.
		
	By:	 	/s/ Janice Burke
		 	Name:	 	Janice Burke
		 	Title:	 	Vice President and General Manager
	
	WENTWORTH INSURANCE COMPANY LTD.
		
	By:	 	/s/ Janice Burke
		 	Name:	 	Janice Burke
		 	Title:	 	Vice President and General Manager



  
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