  Edge lengths of a graph are called flexible if there exist infinitely many
non-congruent realizations of the graph in the plane satisfying these edge
lengths. It has been shown recently that a graph has flexible edge lengths if
and only if the graph has a special type of edge coloring called NAC-coloring.
We address the question how to determine all possible proper flexible edge
lengths from the set of all NAC-colorings of a graph. We do so using
restrictions to 4-cycle subgraphs.

Combinatorics;Robotics;Algebraic Geometry;Metric Geometry