Isolated toughness for fractional (2;b;k)-critical covered graphs

"A graph G is called a fractional (a,b,k)-critical covered graph if for any Q ⊆ V(G) with |Q|=k, G−Q is a fractional a,b-covered graph. In particular, a fractional (a,b,k)-critical covered graph is a fractional (2,b,k)-critical covered graph if a=2. In this work, we investigate the problem of a fractional (2,b,k)-critical covered graph, and demonstrate that a graph G with δ(G)≥3+k is fractional (2,b,k)-critical covered if its isolated toughness I(G)≥1+(k+2)/(b−1), where b and k are nonnegative integers satisfying b≥2+(k/2)."