本文讨论了Ponomarev系统中的一个逆问题.对于Ponomarev系统(f,M,X,P)(或(f,M,X,{Pn})),证明了f是2序列覆盖映射当且仅当P是X的sof网(或每一Pn是X的so覆盖).作为一个推论,本文得到了空间X是度量空间的2序列覆盖映射像(或2序列覆盖π映射像)当且仅当X有sof网(或so覆盖组成的点星网).
This paper investigates an inverse problem in Ponomarev-systems. For a Ponomarev-system (f,M,X,7a) (resp. (f,M,X,{Tan})), we prove that f is a 2-sequence- covering mapping iff P is an sol-network of X (resp. every Pn is an so-cover of X). By these results, we obtain that a space X is a 2-sequence-covering (resp. 2-sequence-covering π-) image of a metric space iff X has an sol-network (resp. a point-star network consisting of so-covers).