Margin note next to theorems

Question

I'm writing a math paper where I would like to give literature references next to theorems using marginnote or marginpar. Unfortunately, I can't seem to get them positioned in the right way (i.e. aligned with the title Theorem x.y) – no matter where I place my macro \mathreferences. Moreover, currently that macro also inserts where it is placed an additional new paragraph that I would like to get rid of without having to always comment out the blank line manually (without the macro, there is no new paragraph). How can I fix this? Any help would be much appreciated!

Here's an MWE:

\documentclass[12pt,a4paper]{memoir}

\usepackage{fontspec}
\usepackage{xunicode}
\usepackage{mathtools}
\usepackage{unicode-math}


\usepackage{amsthm}
\usepackage{thmtools}

\newcounter{mathcounter}
\numberwithin{mathcounter}{chapter}

\declaretheoremstyle[
  spaceabove=2em,
  spacebelow=2em,
  postheadspace=1em,
  headfont=\upshape\bfseries,
  notefont=\mdseries,
  notebraces={(}{)},
  bodyfont=\itshape,
]{mytheoremstyle}

\declaretheorem[
  name={Theorem},
  style=mytheoremstyle,
  numberlike=mathcounter
]{theorem}


\usepackage{xcolor}
\usepackage{marginnote}

\newcommand{\mathreferences}[1]{%
  \marginnote{%
    \footnotesize%
    \normalfont% no italic font, if we're using this inside a theorem
    \color{gray}
    \begin{flushleft}%
    % References: %
    #1%
    \end{flushleft}%
  }%
}


\usepackage{lipsum}
\begin{document}

\chapter{The chapter}
\section{The section}


\begin{theorem}
  \mathreferences{Give some references here}
  \label{foo}

  Let $(M^n, g)$ be a smooth Riemannian manifold, $Σ^{n-1} ⊂ M$ be a
  two-sided embedded hypersurface, possibly with boundary. Let $N$ be
  the – up to a sign unique – normal vector field of $Σ$. Then […]
\end{theorem}

\end{document}

UPDATE: Following the comments, I played around some more and have settled with the following definition of \mathreferences for the time being:

\renewcommand*{\raggedleftmarginnote}{\raggedrightmarginnote}

\newcommand{\mathreferences}[1]{%
  \marginnote{%
    \footnotesize%
    \normalfont% no italic font, if we're using this inside a theorem
    \color{gray}%
    #1%
  }%
}

Redefining \raggedleftmarginnote will always align content of the notes to the left, no matter whether they get displayed on the left or right margin in a double-sided document. (I previously used \begin{flushleft} …\end{flushleft} for this but, unfortunately, this is messing up the vertical positioning.

Unfortunately, I haven't been able to fix the issue with the blank lines, so I have resorted to always commenting out any blank lines following \mathreferences.