Recently, Tan Xuezhong and Liu Bolian in [2] obtained a sufficient condition for the unicyclic graphs with nullity 0 and asked a problem that if this condition is also necessary.

• 在文献[2]中作者给出了刻画非奇异单圈图的充分条件，并提出了一个问题，即这个条件是否也是必要的。