Here is my Latex file:
\documentclass[10pt, a4paper]{amsart}
\usepackage{amsmath, amssymb,amsthm}
\usepackage{lettrine}
\usepackage[Sonny]{fncychap}
\usepackage{url}
\usepackage[english]{babel}
\usepackage{amsmath, amssymb,amsthm}
\usepackage[all]{xy}
\usepackage{tabularx}\renewcommand {\theenumi}{\roman{enumi}}
\usepackage[applemac]{inputenc}
\usepackage{graphicx}
\usepackage[dvipsnames]{xcolor}
\usepackage{geometry}
\usepackage{hyperref}
\usepackage{url}
\usepackage[applemac]{inputenc}
\usepackage{enumitem}
\begin{document}
This is my latex file. I want to cite \cite{stackexchange}.
\bibliography{biblio}
\bibliographystyle{alpha}
\newpage
\end{document}
Here is biblio.bib:
@misc{stackexchange,
title = {{R}eal units of the cyclotomic number fields of an odd prime order},
howpublished = "\url{https://math.stackexchange.com/questions/175063/real-units-of-the-cyclotomic-number-fields-of-an-odd-prime-order}",
author={{S}tack Exchange user {M}att {E}}
}
As a result, the reference is printed out wrongly, with large spaces between each word. You can see the result on the following screenshot.

Thanks for your help
urland/orhyperrefpackage? – Mico Feb 16 '18 at 11:38