The reactivity of substituted purines in strongly basic medium ; the occurence of geometrical isomerism in the anions of aromatic amino compounds / [by] N.J. KosSynthesis and amination of naphthyridines / H.J.W. van den HaakIntramolekulêre omskakelings by aminerings van halogeenpiridiene en etoksihalogeenpiridiene / Matthys Johannes Pieterse