A 5-D hyperchaotic Rikitake dynamo system with hidden attractors S. Vaidyanathan, V.-T. Pham and C.K. Volos Eur. Phys. J. Special Topics, 224 8 (2015) 1575-1592 Published online: 27 July 2015 DOI: 10.1140/epjst/e2015-02481-0