Some elementary Ramanujan graphs
The published version is located at http://www.springerlink.com/content/u20164219h133851/
We give elementary constructions of two infinite families of Ramanujan graphs of unbounded degree. The first uses the geometry of buildings over finite fields, and the second uses triangulations of modular curves.
PE Gunnells. "Some elementary Ramanujan graphs" Geometriae Dedicata 112.1 (2005): 51-63.
Available at: http://works.bepress.com/paul_gunnells/10
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