# Dynkin diagrams question

A MathOverflow user had some trouble asking on MathOverflow about how to draw the Dynkin diagrams from pages 56 and 57 of Humphrey's book Introduction to Lie Groups and Representation Theory. He seems to be unclear how to ask here, so I thought I would ask (and answer) his question myself. How do you draw those diagrams?

\documentclass{amsart}
$\begin{array}{cc} A_1 \times A_1 & \dynkin{A}{1}\dynkin{A}{1}\\ A_2 & \dynkin{A}{2}\\ B_2 & \dynkin{B}{2}\\ G_2 & \dynkin{G}{2} \end{array}$
$\begin{array}{cc} B_2 & \dynkin{B}{2}\\ G_2 & \dynkin{G}{2} \end{array}$