#!/usr/bin/php

<pre>@inproceedings{ISWC-2018-optional,
  author    = {Guohui Xiao and
               Roman Kontchakov and
               Benjamin Cogrel and
               Diego Calvanese and
               Elena Botoeva},
  title     = {Efficient Handling of {SPARQL} {OPTIONAL} for {OBDA}},
  booktitle = {Proc. of the 17th International Semantic Web Conference ({ISWC} 2018)},
  series    = {Lecture Notes in Computer Science},
  volume    = {11136},
  pages     = {354--373},
  publisher = {Springer},
  year      = {2018},
  webpdf = {https://www.doc.ic.ac.uk/~ebotoeva/papers/xkccb-ISWC-18.pdf},
}</pre>