Surender Baswana Akshay Gaur Sandeep Sen Jayant Upadhyay Distance Oracles for Unweighted Graphs: Breaking the Quadratic Barrier with Constant Additive Error. 609-621 2008 ICALP (1) http://dx.doi.org/10.1007/978-3-540-70575-8_50 conf/icalp/2008-1 db/conf/icalp/icalp2008-1.html#BaswanaGSU08