I have almost the same question as this, except I am using BibLatex. I would like the size of 'References' to be the same size as the title of 'Problem 1' of the subsection in the document. I tried the suggested change in the linked question, but it did not work for me.
\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage[]{amsthm}
\usepackage[]{amssymb} %gives us the character \varnothing
\usepackage{amsmath}
\usepackage{commath}
\usepackage{indentfirst}
\usepackage{hyperref} %lets us use links
\hypersetup{%
bookmarksnumbered=true,%
bookmarks=true,%
colorlinks=true,%
linkcolor=blue,%
citecolor=blue,%
filecolor=blue,%
menucolor=blue,%
urlcolor=blue,%
pdfnewwindow=true}
\usepackage[backend=biber,
style=alphabetic,
sorting=nyt]{biblatex}
\addbibresource{bib.bib}
\begin{document}
\newtheorem{lem}{Lemma}
\newtheorem{thm}{Theorem}
\newtheorem{cor}{Corollary}
\maketitle
\subsection*{Problem 1}
Blah blah blah blah.
\printbibliography
\end{document}