Xie-Nie's Stability Criterion

Xie Xukai(Hsieh Hsük'ai) and Nie Yiyong (Nieh Yiyung) Criterion had been proposed much earlier than the similar ones in foreign countries.But it was unknown to the public owing to some historical reasons.A brief mention of that in this journal last year(Vol.10,No.1,1981) has aroused great interest and attention among readers in China.On their request,a more detailed exposition of the criterion is given