Model Theory and Algebra : A Memorial Tribute to Abraham Robinson On recursively saturated models of arithmetic A note on existentially complete division rings Ideals of integers in nonstandard number fields Categories of local functors Impredicativity of the existence of the largest divisible subgroup of an Abelian p group Elementary equivalence classes of generic structures and existentially complete structures The number of equivalence classes of existentially complete structures Finite forcing and generic filters in arithmetic Dense embeddings I: A theorem of Robinson in a general setting New facts about Hilberts seventeenth problem Nonstandard aspects of Hilberts irreducibility theorem Projective model theory and coforcing On algebraic curves over commutative regular rings Existence of rigid like families of Abelian p groups The complexity of Tf and omitting types in FT Model completeness and skolem expansions.