Allen RH, Stabler SP, Lindenbaum J (noiembrie 1993). „Serum betaine, N,N-dimethylglycine and N-methylglycine levels in patients with cobalamin and folate deficiency and related inborn errors of metabolism”. Metabolism. 42 (11): 1448–60. doi:10.1016/0026-0495(93)90198-W. PMID7694037.
Allen RH, Stabler SP, Lindenbaum J (noiembrie 1993). „Serum betaine, N,N-dimethylglycine and N-methylglycine levels in patients with cobalamin and folate deficiency and related inborn errors of metabolism”. Metabolism. 42 (11): 1448–60. doi:10.1016/0026-0495(93)90198-W. PMID7694037.