A region crossing change is a local transformation on a knot or link diagram. We show that a region crossing change on a knot diagram is an unknotting operation, and we define the region unknotting number for a knot diagram and a knot.
Ayaka SHIMIZU. "Region crossing change is an unknotting operation." J. Math. Soc. Japan 66 (3) 693 - 708, July, 2014. https://doi.org/10.2969/jmsj/06630693