## Description

_Describe your pull request here._

## Legal notice (do not delete)

Thank you for your contribution to the Zeta library.

It is required that contributors assign copyright to the original author so that he retains full ownership of the project. This makes it easier for other entities to use the software because they only have to deal with one copyright holder. It also gives the original author assurance that he will be able to make decisions in the future without gathering and consulting all contributors.

While this may seem odd, many open source maintainers practice this.

By submitting this PR, you agree to the following:

> You hereby assign copyright in this PR's code to the Zeta library and its copyright holder, Manuel Sainz de Baranda y Goñi, to be licensed under the same terms as the rest of the code. You agree to relinquish any and all copyright interest in the software, to the detriment of your heirs and successors.
