@article{Fredi1998MinimalOG,
title={Minimal Oriented Graphs of Diameter 2},
author={Zolt{\'a}n F{\"u}redi and Peter Hor{\'a}k and Chandra M. Pareek and Xuding Zhu},
journal={Graphs and Combinatorics},
year={1998},
volume={14},
pages={345-350}
}

Let f n be the minimum number of arcs among oriented graphs of order n and diameter 2. Here it is shown for n > 8 that 1ÿ o 1n log nU f nU n log nÿ 3=2n. 1. Oriented chromatic number An oriented graph is a digraph without opposite arcs, i.e., every pair of vertices is connected by at most one arc. An oriented colouring of an oriented graph D is a colouring of its vertices so that every colour class is an independent set, moreover for any two colour classes U and V , all the arcs… CONTINUE READING