Bailey, Regan, James Mills, Elizabeth Yetley, Jaime Gahche, Chrisitne Pfeiffer, Johanna Dwyer, Kevin Dodd, Christopher Sempos, Joseph Beth, and Mary Frances Picciano. 2012. “Serum Unmetabolized Folic Acid in a Nationally Representative Sample of Adults ≥ 60 Years in the United States, 2001-2002”. Food & Nutrition Research, April. https://doi.org/10.3402/fnr.v56i0.5616.