\documentclass[10pt,a5paper]{article} \usepackage[utf8]{inputenc} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage[left=2cm,right=2cm,top=2cm,bottom=2cm]{geometry} \begin{document} \cite{knuth68} You can find my results in \cite{th} We can also refer to this book \cite{rudin} \bibliographystyle{alpha} \bibliography{my_biblio} \end{document}