A Method for the Quantitative Determination of Anthraquinones and Alkaloids in Cell and Tissue Cultures of Cinchona Sp. - Wijnsma, R; van Vliet, T B; Harkes, P A A; van Groningen, H J; van der Heijden, R; Verpoorte, R; Svendsen, A Baerheim (Planta Medica, 1987)