Doctoral thesis (2003) - VS Massingue (author) , M Looijen (promotor) , TMA Bemelmans (copromotor) , W Gerhardt-Hackl (copromotor) , AA Holtgrefe (copromotor) , N Matos (copromotor) , B Mutagahywa (copromotor) , K Smit (copromotor) , H. Koppelaar (copromotor)