# Math Help - The product log is not elementary

1. ## The product log is not elementary

The product logarithm (Lambert W) is the inverse of $f(z) = z e^z$. Wikipedia claims it is not elementary, but gives no reference. How do we know that is not elementary?

The product logarithm (Lambert W) is the inverse of $f(z) = z e^z$. Wikipedia claims it is not elementary, but gives no reference. How do we know that is not elementary?