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\begin{document}

\begin{letter}%
{To the Editors of the Journal of Physical Chemistry Letters}

\opening{Dear Editors,}

\justifying
Please find enclosed a revised version of our invited \textit{Perspective} manuscript entitled
\begin{quote}
\textit{``The Bethe-Salpeter Equation Formalism: From Physics to Chemistry''}.
\end{quote}
We would to thank the reviewers for their constructive comments.
Our detailed responses to their comments can be found below.
For convenience, all modifications and changes are highlighted in red in the revised version of the manuscript. 

Note that the abstract has been shorten to less than 150 words, the section headings have been removed, and the references have been checked and use the JPCL formatting.

We look forward to hearing from you.

\closing{Sincerely, the authors.}

\newpage

%%% REVIEWER 1 %%%
\noindent \textbf{\large Authors' answer to Reviewer \#1}

\begin{enumerate}
        \item 
        \textbf{Reviewer's comment}
        \\
	\textit{The rhs of eq.~(9) does not depend on the coordinate 1. Then, in eq.~(8), there is no coordinate 3 to integrate over. Is there a misprint here?}
	\\
	\\
	\textbf{Authors' response} 	
	\\
	Yes, there's a misprint. This has been fixed.
	\\
	\\
	
	\item  
	\textbf{Reviewer's comment} 
	\\
	\textit{Ref.~111 is wrong. The correct reference is: https://doi.org/10.1063/1.5051028}
	\\
	\\
	\textbf{Authors' response} 
	\\
	Sorry about this. The reference has been corrected.
	\\
	\\
	
	\item
	\textbf{Reviewer's comment} 
	\\		
	\textit{Page 3, 2nd column, line 7: reduce}
	\\
	\\
	\textbf{Authors' response} 
	\\
	This has been fixed.
	\\
	\\

	\item
	\textbf{Reviewer's comment} 
	\\
	\textit{Page 3, 2nd column, line  42: 4-point}
	\\
	\\
	\textbf{Authors' response} 
	\\
	This has been fixed.
	\\
	\\

	\item
	\textbf{Reviewer's comment} 
	\\
	\textit{Page 6, 2nd column, 6th line from bottom: plague}
	\\
	\\
	\textbf{Authors' response} 
	\\
	This has been fixed.
	\\
	\\
	
	\item
	\textbf{Reviewer's comment} 
	\\
	\textit{Page 7, 2nd column, 11th line from bottom: double excitations}
	\\
	\\
	\textbf{Authors' response} 
	\\
	This has been fixed.
	\\
	\\	
\end{enumerate}

\newpage

%%% REVIEWER 2 %%%
\noindent \textbf{\large Authors' answer to Reviewer \#2}

\begin{enumerate}

	\item
	\textbf{Reviewer's comment} 
	\\
	\textit{GW and BSE are based on the key issue of screening. Physicists will
immediately identify this as the central topic of macroscopic 
electrodynamics (or rather electrostatics, because retardation and 
magnetic fields are left out), and realize that all the common knowledge
of classical electrostatics apply. For chemists without such background 
these links might not be so obvious, and it might be helpful to at least 
mention this somewhere, maybe in connection with Eq.~(8).}
	\\
	\\
	\textbf{Authors' response} 
	\\
	We thank the review for this helpful comment.
	Accordingly, we have added a new paragraph below Eq.~(8) to mention this.
	\\
	\\

	\item
	\textbf{Reviewer's comment} 
	\\
	\textit{As the authors point out, starting from KS energies (and thus from a 
too small band gap) usually leads to GW energies that still underestimate 
the band gap, and some self-consistency (maybe in the energies) or a
hybrid-functional starting point are required to cure this problem.
To my understanding the underlying reason is that a too small initial gap
produces too strong dielectric screening, and this produces too weak 
quasiparticle corrections. The authors might consider to include this in 
the discussion of Sec. 3.}
	\\
	\\
	\textbf{Authors' response} 
	\\
	Thank you again for yet another useful comment.
	We have added a small paragraph below Eq.~(26) to highlight this practical fact.
	\\
	\\
	
	\item
	\textbf{Reviewer's comment} 
	\\
	\textit{I believe that there are several index errors in the equations, for 
instance Eq.~(5): $f_s(r')$ inside the integral,  Eq.~(8): $v(1,3)$,
Eq.~(9):  $G(1,3)$. The authors should check all equations.}
	\\
	\\
	\textbf{Authors' response} 
	\\
	Sorry for the mistakes. These equations have been corrected.
	\\
	\\
	
	
	\end{enumerate}

\end{letter}
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