This paper deals with the problem of the estimation of regions of asymptotic stability for continnons, antonomom, nonlinear systems. The first part of the work provides a comprehensive survey of the existing methods and of their applications in engineering fields. In the serond part certain topological considerations are first developed and the "trajectory reversing method" is then presented together with a theorem on which it is based. In the final part, several examples of application are reported, showing the efficiency of the proposed technique for low-order (second and third) systems. A. Zubov Methods The contributions included in this set refer to the Zubov theorem [5]-[7l which gives necessary and sufficient conditions

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Tubal factor infertility may be reversed using porcine small-intestinal submucosa (SIS). The method uses as a model the New Zealand White rabbit uerine horn. In surgery, SIS grafts were prepared from porcine jejunum; the uterine horn segment was resected and a graft was placed; then the contralateral adnexa was resected. Fecundability was tested with natural mating. Three out of six rabbits became pregnant. Gross and microscopic examination confirmed regeneration of all tissue layers. Thus, this study determined that SIS facilitates successful regeneration of uterine horn morphology in a manner similar to that observed in other tissues and species.