Exhibit 12

Statement re: Calculation of Ratios of Earnings to
Combined Fixed Charges and Preferred Stock Dividends
(Dollars in thousands)

	Three Months Ended March 31, 2006		Year Ended December 31, 2005		Year Ended December 31, 2004		Year Ended December 31,  2003		Year Ended December 31, 2002		Year Ended December 31, 2001
Net income from continuing operationsless preferred distributions	$	14,032	$	93,511	$	110,945	$	114,620	$	120,725	$	178,529
Preferred distributions	12,712		46,479		33,777		37,321		45,053		52,442
Minority interest in earnings of common unitholders	1,253		9,400		11,608		12,426		12,958		24,844
Interest expense	38,655		119,640		109,297		100,047		86,844		82,570
Earnings before fixed charges	$	66,652	$	269,030	$	265,627	$	264,414	$	265,580	$	338,385
Interest expense	$	38,655	$	119,640	$	109,297	$	100,047	$	86,844	$	82,570
Interest costs capitalized	5,580		9,510		5,961		6,734		13,529		25,859
Total fixed charges	$	44,235	$	129,150	$	115,258	$	106,781	$	100,373	$	108,429
Preferred distributions	$	12,712	$	46,479	$	33,777	$	37,321	$	45,053	$	52,442
Total fixed charges and preferred distributions	$	56,947	$	175,629	$	149,035	$	144,102	$	145,426	$	160,871
Ratio of Earnings to Fixed Charges	1.51		2.08		2.30		2.48		2.65		3.12
Ratio of Earnings to Combined Fixed Charges and Preferred Distributions	1.17		1.53		1.78		1.83		1.83		2.10