FACTA UNIVERSITATIS SERIES MATHEMATICS AND INFORMATICS, Vol. 18, 2003 Contents B. S. Popov and H. M. Srivastava  LINEARIZATION OF A PRODUCT OF TWO POLYNOMIALS OF DIFFERENT ORTHOGONAL SYSTEMS G. V. Milovanović and M. Stanić  CONSTRUCTION OF MULTIPLE ORTHOGONAL POLYNOMIALS BY DISCRETIZED STIELTJES-GAUTSCHI PROCEDURE AND CORRESPONDING GAUSSIAN QUADRATURES G.  V. Milovanović and A. S. Cvetković  AN APPLICATION OF LITTLE 1/Q-JACOBI POLYNOMIALS TO SUMMATION OF CERTAIN SERIES H. H. Khan and G. Ram  ON THE DEGREE OF APPROXIMATION D. Stojanović and S. Djordević-Kajan  MODELING MOBILE POINT OBJECTS IN LOCATION-BASED SERVICES