References about Hasse diagrams of root systems

Hasse diagrams for root systems can be extracted from the following paper, which can be found on E. Plotkin's publication page:

• E.Plotkin, A.Semenov, N.Vavilov, Visual basic representations: An atlas, Int.Journal of Algebra and Computation, 8 (1998), no. 1, 61-95.

The paper discusses more generally Hasse diagrams for the weights of various representations and various applications. The pictures for the adjoint representations give the Hasse diagram of the root system (but using all roots, not just the positive ones).

I put a LaTeX package up on CTAN today to draw the Hasse diagrams of all root systems, following Ringel's pictures. Code is as simple as

\documentclass{amsart}
\usepackage{lie-hasse}
\begin{document}
\hasseDiagrams{A4;B5}
\hasseDiagrams{F4;G2}
\end{document}

to display