Becker ML, Gaedigk R, van Haandel L, Thomas B, Lasky A, Hoeltzel M, Dai H, Stobaugh J, Leeder JS. The effect of genotype on methotrexate polyglutamate variability in juvenile idiopathic arthritis and association with drug response. Arthritis Rheum. 2011 Jan; 63(1):276-85.