The problem of relevant detail, S. Levin; models for the spread of universally fatal diseases, F. Brauer; non-existence of periodic solutions for a class of epidemiological models, S. Busenberg and P. van den Driesche; an S-E-I epidemic model with varying population size, A. Pugliese; stability change of the endemic equilibrium in age-structured models for the spread of S-I-R type infectious diseases, H. Thieme; a mathematical model for the dynamics of a phytoplankton population, E. Beretta and A. Fasano; some delay models for juvenile versus adult competition, J. Cushing.