1. Tumour–stromal interactions generate emergent persistence in collective cancer cell migration by William K. Chang, Carlos Carmona-Fontaine, and Joao B. Xavier Interface Focus Volume 3(4):20130017 August 6, 2013 ©2013 by The Royal Society

2. (a) Cell–cell interactions in the cancer–stromal model of self-propelled particles. William K. Chang et al. Interface Focus 2013;3:20130017 ©2013 by The Royal Society

3. Global order parameter as a function of noise in a system with cyclic boundary conditions. William K. Chang et al. Interface Focus 2013;3:20130017 ©2013 by The Royal Society

4. (a) Comparison of a system with cyclic boundary conditions with an unbounded system. William K. Chang et al. Interface Focus 2013;3:20130017 ©2013 by The Royal Society

5. (a) Time course of mean displacement of cells in the system. William K. Chang et al. Interface Focus 2013;3:20130017 ©2013 by The Royal Society

6. (a) Clusters incorporating at least one stromal cell are considered stromalized. William K. Chang et al. Interface Focus 2013;3:20130017 ©2013 by The Royal Society