Obtaining variable references in an expression

What is the best way to obtain the variable references in an expression?

For instance, from:

x = y + 10 * z

I want to obtain:

x, y, z

I realise this could be done through an AST visit, but I wondered if there
is a way I could do it through the existing API?

I'd suggest a RecursiveASTVisitor.

-Eli