... perturbations of the differential equation y 0 and the analogous difference equation,” Journal of Mathematical Analysisand Applications, vol. 169, no. 2, pp. 437–452, 1992.8 R. Spigler and ... second author thanks Liu Bie Ju Center for Mathematical Science and Department of Mathematics of City University of Hong Kong for their hospitality. This work is partiallysupported by the National ... Gy¨ori, and G. Ladas, Eds., pp. 567–577, Gordon and Breach, Amsterdam, The Netherlands,1997.10 C. M. Bender and S. A. Orszag, Advanced Mathematical Methods for Scientists and Engineers,International...