@misc{engel2015semi,
  title={Semi-dense simultaneous localization and mapping},
  author={Engel, J. and Sturm, J. and Cremers, D.},
  url={http://google.com/patents/WO2015043872A1?cl=ko},
  year={2015},
  month={Apr.},
  note={WO Patent App. PCT/EP2014/068,338}
}