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