Sanchez-Guerrero J , Liang MH , Karlson EW , Hunter DJ , Colditz GA.Postmenopausal estrogen therapy and the risk for developing systemic lupus erythematosus . Ann Intern Med1995; 122: 430-433 .
2.
Meier CR , Sturkenboom MC , Cohen AS , Jick H.Postmenopausal estrogen replacement therapy and the risk of developing systemic lupus erythematosus or discoid lupus . J Rheumatol1998; 25: 1515-1519 .
3.
Cooper GS , Dooley MA , Treadwell EL , St. Clair EW , Gilkeson GS.Hormonal and reproductive risk factors for development of systemic lupus erythematosus . Arthritis Rheum2002; 46: 1830-1839 .
4.
Buyon JP , Petri MA , Kim MYet al.The effect of combined estrogen and progesterone hormone replacement therapy on disease activity in systemic lupus erythematosus: a randomized trial . Ann Intern Med2005; 142: 953-962 .
5.
Walker AM.Confounding by indication . Epidemiology1996; 7: 335-336 .
6.
Listing J , Strangfeld A , Kary Set al.Infections in patients with rheumatoid arthritis treated with biologic agents . Arthritis Rheum2005; 52: 3403-3412 .
7.
Khanna D , Park GS , Paulus HEet al.Reduction of the efficacy of methotrexate by the use of folic acid: post hoc analysis from two randomized controlled studies . Arthritis Rheum2005; 52: 3030-3038 .
8.
Rosenbaum PR , Rubin DB.The central role of the propensity score in observational studies for causal effects . Biometrics1983; 70: 41-55 .
9.
Rubin DB.Estimating causal effects from large data sets using propensity scores . Ann Intern Med1997; 127: 757-763 .
10.
D’Agostino RB, Jr.Propensity score methods for bias reduction in the comparison of a treatment to a non-randomized control group . Statist Med1998; 17: 2265-2281 .