BibTex format
@article{Haddaway:2015:10.1371/journal.pone.0138237,
author = {Haddaway, NR and Collins, AM and Coughlin, D and Kirk, S},
doi = {10.1371/journal.pone.0138237},
journal = {PLoS ONE},
title = {The role of Google Scholar in evidence reviews and its applicability to grey literature searching},
url = {http://dx.doi.org/10.1371/journal.pone.0138237},
volume = {10},
year = {2015}
}