perturbations of selfadjoint operators.- On surfaces defined by ordinary differential equations: A new approach to Hilbert¿s 16th problem.- Self-adjointness for general elliptic operators with Sobolev-type coefficients.- On a Nehari¿s constant.- Asymptotics of eigenvalues for some "non-definite" elliptic problems.- Optimal control of a system governed by hyperbolic operator.- A global study of a hamiltonian system with multi turning points.- Some further results on oscillatory behavior of solutions of nth order delay differential equations.- A model for a myelinated nerve axon.- Spatial patterning of the spruce budworm in the presence of defoliation.- Vector models for infectious diseases.- Multi- dimensional reaction-convection-diffusion equations.- On periodic solutions of forced second order differential equations with a deviating argument.- The theory of quasi periodic motions.- Stability criteria for linear integro- differential equations.- A mechanical model for biological pattern formation: A nonlinear bifurcation analysis.- Almost surely non-linear solutions of stochastic linear delay equations.- Properties of the set of global solutions for the cauchy problems in a locally convex topological vector space.- Boundary value problems for forced nonlinear equations at resonance.- Periodic-solutions of prescribed period for hamiltonian systems.- Bursting oscillations in an excitable membrane model.- Semilinear second order evolution equations and regular boundary conditions.- Symmetry-breaking for semilinear elliptic equations.- On a boundary value problem associated with some difference-differential equations.- A-proper maps and bifurcation theory.- On the singularities and asymptotic expansions of singular sturm- liouville expansions.