Graceful signed graphs
A -sigraph is an ordered pair where is a -graph and is a function which assigns to each edge of a positive or a negative sign. Let the sets and consist of positive and negative edges of , respectively, where . Given positive integers and , is said to be -graceful if the vertices of can be labeled with distinct integers from the set such that when each edge of is assigned the product of its sign and the absolute difference of the integers assigned to and the...