“Malic acid supplementation increases urinary citrate excretion and urinary pH: implications for the potential treatment of calcium oxalate stone disease”. Journal of endourology28 (2). (2014). doi:10.1089/end.2013.0477. PMID24059642.
Karlheinz Miltenberger "Hydroxycarboxylic Acids, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry,2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a13 507
“Malic acid supplementation increases urinary citrate excretion and urinary pH: implications for the potential treatment of calcium oxalate stone disease”. Journal of endourology28 (2). (2014). doi:10.1089/end.2013.0477. PMID24059642.