by Oleg Pikhurko, Helmut Veith, Oleg Verbitsky
Reference:
The first order definability of graphs: Upper bounds for quantifier depthOleg Pikhurko, Helmut Veith, Oleg VerbitskyDiscrete Applied Mathematics, volume 154, number 17, pages 2511-2529, 2006.
Bibtex Entry:
@article{DBLP:journals/dam/PikhurkoVV06,
author = {Oleg Pikhurko and Helmut Veith and Oleg Verbitsky},
title = {The first order definability of graphs: Upper bounds for quantifier
depth},
number = {17},
year = {2006},
journal = {Discrete Applied Mathematics},
pages = {2511--2529},
volume = {154},
url = {http://dx.doi.org/10.1016/j.dam.2006.03.002}
}