luispedro

\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}

\node (theta) at (0,0) [circle, draw] {$\theta$};
\node (z) at (2,0) [circle, draw] {$z$};
\node (w) at (4,0) [circle, draw] {$w$};
\node (alpha) at (1,2) [circle, draw] {$\alpha$};