1. Bognar A (1981) Dtsch Lebensm Rundsch 77:431?436
2. Bognar A (1989) BFE-Bericht, R-89-01, 9?16, Karlsruhe
3. Just K (1991) Diploma thesis, University Giessen, 83?91
4. Hollmann PCH, Slangen JH (1991) Final report on the first BCR intercomparison on the determination of vitamins in food. Brussels, pp 42?43