1. Determination of retinyl esters and retinol in serum or plasma by normal phase liquid chromatography: methods and applications;Bankson;Clin. Chem.,1986
2. Hypocarotenemia in patients fed enterally with commercial liquid diets;Bowen;J. Paren. Enteral Nutr.,1988
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4. Lack of improvement in vitamin A status with increased consumption of dark-green leafy vegetables;de Pee;Lancet,1995
5. Simultaneous determination of retinol and retinyl esters in serum or plasma by reversed-phase-high-performance-liquid-chromatography;DeRuyter;Clin. Chem.,1978