. 2022 Apr 27;478(2260):20210828. doi: 10.1098/rspa.2021.0828
© 2022 The Authors.
Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
Figure 6.
Contraction of two vertices.