@inproceedings{Fister2015ModifiedQuaternion,
  title={Modified bat algorithm with quaternion representation},
  author={Fister, Iztok and Brest, Janez and Fister Jr, Iztok and Yang, Xin-She},
  booktitle={IEEE Congress on Evolutionary Computation},
  pages={491--498},
  year={2015},
  organization={IEEE}
}