Every signed planar graph without cycles of length from 4 to 8 is 3-colorable

In this paper, we investigate the signed graph version of Erdös problem: Is there a constant c such that every signed planar graph without k-cycles, where 4≤k≤c, is 3-colorable and prove that each signed planar graph without cycles of length from 4 to 8 is 3-colorable.