I am looking to create a reference list where I can choose to have references numbered as 1 (a), 1(b) etc. instead of [1], [2] etc. I would ideally like my ref 6 and 7 to be labelled as 6 (a), 6 (b) with rest labelled as 1, 2 etc.

Is there a way I can do this? I am a beginner in Tex so please ignore some of my silly errors. Here is the MWE and the 7 references I have used. I am sorry for the long MWE, I am using my university template.

Thank you so much for your help and time.



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%--------------------preference packages------------





% \usepackage{achemso}
% \setkeys{acs}{etalmode = truncate, maxauthors = 2,usetitle = true,doi=true}

 % linkdoi    = false,
 % mciteplus  = true,
 % maxauthors = 0,
  %usetitle   = true,
  %usedoi     = true,
  %super      = true



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%-----------------------fonts ----------------------
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% \usepackage[default]{gillius}
% \usepackage[sc]{mathpazo}
% \linespread{1.05} % Palladio needs more leading (space between lines)
% \usepackage[T1]{fontenc}
% \usepackage{stix}
\renewcommand{\rmdefault}{phv} % Arial
\renewcommand{\sfdefault}{phv} % Arial




 {\chaptertitlename\ \thechapter}{20pt}{\huge}

% \titleformat{\section}




\usefont{T1}{qhv}{b}{n}\selectfont\color{black}} % "qhv" - TeX Gyre Heros, "b" - bold
{\hspace{-0.4pt}\large \thesection\hspace{0.6em}}

\settowidth{\longestlabel}{ viii.}
\settasks{counter-format={tsk[r].}, label-format={}, label-width=\longestlabel,
item-indent=0pt, label-offset=2pt, column-sep={10pt}}

\newcommand{\QuestionNB}{\arabic{Question}.\ }
% \renewcommand{\ExerciseName}{EXERCISES}
\renewcommand{\ExerciseHeader}{\noindent\def\stackalignment{l}% code from https://tex.stackexchange.com/a/195118/101651
{\noindent\textcolor{flint}{\textbf{CHAPTER \thechapter}}\newline%
\noindent\bfseries\emph{\textcolor{flint}{\AnswerName\ \ExerciseHeaderNB, page %
% {\noindent\bfseries\emph{\textcolor{flint}{\AnswerName\ \ExerciseHeaderNB, page \pageref{\AnswerRef}}}\smallskip}

\usepackage{tikz} %TikZ is required for this to work. Make sure this exists before the next line
\usepackage{tikz-3dplot} %requires 3dplot.sty to be in same directory, or in your LaTeX installation
% \usetkzobj{all}
% \usepackage{pgfplots}
% % \usepgfplotslibrary{external}
% % \tikzexternalize
% \pgfplotsset{compat=1.12}
% \usepackage[active,tightpage]{preview} %generates a tightly fitting border around the work
% % \PreviewEnvironment{tikzpicture}
% % \setlength\PreviewBorder{2mm}

% \usepackage{footmisc}
% \renewcommand{\thefootnote}{\fnsymbol{footnote}}
% \newfloat{Scheme}{htbp}{los}[section]

\usepackage{pgfplots, pgfplotstable, filecontents}
\pgfplotsset{scaled y ticks=false}
\pgfplotsset{scaled x ticks=false}
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25 div exch
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dup abs add 2.0 div
%% matte-ify
0.6 mul 0.4 add
%% currently there is just one number in the stack.
%% we need three corresponding to the RGB values

% Requires \usetikzlibrary{calc}
% #1: starting node
% #2: ending node
% #3: attributes for the shape connecting nodes
\path let
 \p1 = ($\left(#2)-(#1\right)$),
 \n1 = {veclen(\p1)},
 \n2 = {atan2(\x1,\y1)} % <- Update
 (#1) -- (#2) node[#3, midway, sloped, shading angle=\n2+90, minimum width=\n1+1, inner sep=0pt, #3] {};


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% % for formal definitions
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 \noindent\hspace{-4.55pt}% disable indenting first paragraph

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\newcommand{\tc}{$T_{\textrm{\sc{c}}} $ }

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% \counterwithout{equation}{subsection}
% \counterwithout{equation}{subsubsection}

% \usepackage{showframe}
% \usepackage{layout}


% \affil{University of Sussex}


%-------To do------------
% Ctrl r: Schrodinger Schr\"{o}dinger

I have one reference here.\cite{Das2017} I have two more references here.\cite{savoie2015,kordnezhadian2022}

My third reference is here.\cite{kordnezhadian2022}

Fourth\cite{matsumoto2018} and 5th reference.\cite{rueping2017}

\section{Aims and Objectives}

No reference in this section
\section{Scientific Approach/Methodology}

Two references here.\cite{Mayr2008,mayrdatabase} 


No refs here.


Bibliography files
author = {Reza Kordnezhadian and Bing‐Yu Li and Armir Zogu and Joachim Demaerel and Wim M. De Borggraeve and Ermal Ismalaj},
doi = {10.1002/chem.202201491},
file = {::},
issn = {0947-6539},
journal = {Chem. – A Eur. J.},
month = {oct},
number = {60},
title = {{Chemistry of Pentafluorosulfanyl Derivatives and Related Analogs: From Synthesis to Applications}},
url = {https://onlinelibrary.wiley.com/doi/10.1002/chem.202201491},
volume = {28},
year = {2022},
pages = {1-26}

author = {Paul R. Savoie and John T. Welch},
doi = {10.1021/cr500336u},
file = {::},
issn = {0009-2665},
journal = {Chem. Rev.},
month = {jan},
number = {2},
pages = {1130--1190},
title = {{Preparation and Utility of Organic Pentafluorosulfanyl-Containing Compounds}},
url = {https://pubs.acs.org/doi/10.1021/cr500336u},
volume = {115},
year = {2015}

abstract = {A protocol for the fast and selective two-electron reduction of the potent greenhouse gas sulfur hexafluoride (\ce{SF6}) by organic electron donors at ambient temperature has been developed.},
author = {Magnus Rueping and Pavlo Nikolaienko and Yury Lebedev and Alina Adams},
doi = {10.1039/C7GC00877E},
file = {::},
issn = {1463-9262},
journal = {Green Chem.},
number = {11},
pages = {2571--2575},
title = {{Metal-free reduction of the greenhouse gas sulfur hexafluoride, formation of \ce{SF5}-containing ion pairs and the application in fluorinations}},
url = {http://xlink.rsc.org/?DOI=C7GC00877E},
volume = {19},
year = {2017}

   author = {Prajwalita Das and Etsuko Tokunaga and Norio Shibata},
   journal = {Tetrahedron Lett.},
   title = {Tetrahedron Letters Recent advancements in the synthesis of pentafluorosulfanyl (SF 5 )-containing heteroaromatic compounds},
   url = {https://doi.org/10.1016/j.tetlet.2017.11.015},
   year = {2017},
   pages = {4803},
   volume = {58}

   author = {Kazuhiko Matsumoto and Yuki Haruki and Shunsuke Sawada and Shigeyuki Yamada and Tsutomu Konno and Rika Hagiwara},
   doi = {10.1021/acs.inorgchem.8b02655},
   issn = {0020-1669},
   issue = {23},
   journal = {Inorg. Chem.},
   month = {12},
   pages = {14882-14889},
   title = {Stabilization of SF 5 – with Glyme-Coordinated Alkali Metal Cations},
   volume = {57},
   url = {https://pubs.acs.org/doi/10.1021/acs.inorgchem.8b02655},
   year = {2018},

   abstract = {Comprehensive nucleophilicity scales including π-, n- and σ-nucleophiles have been constructed using benzhydrylium ions and structurally related quinone methides as reference electrophiles. It is shown how the correlation (Eqn (1)) log k20°C = s(E + N), where s and N are nucleophile-specific parameters and E is an electrophile-specific parameter, has recently been employed to characterize further classes of nucleophiles (phosphines, amines, isonitriles, trifluoro-methanesulfonyl- substituted carbanions) and electrophiles (2-benzylideneindan-1,3-diones and benzylidenebarbituric acids). Practical applications of the reactivity parameters E, N and s for developing Friedel-Crafts alkylations in neutral alcoholic or aqueous solution and for characterizing nucleophilic organocatalysts will be discussed. Eventually, a new correlation equation will be presented, which includes Eqn (1), the Ritchie equation (nucleophilic additions to stabilized carbocations), and the Swain-Scott equation (nucleophilic substitutions of methyl halides) as special cases. Copyright © 2008 John Wiley & Sons, Ltd.},
   author = {Herbert Mayr and Armin R. Ofial.},
   doi = {10.1002/poc.1325},
   issn = {08943230},
   issue = {7-8},
   journal = {J. Phys. Org. Chem.},
   keywords = {Electrophilicity,Intrinsic barriers,Kinetics,Linear free energy relationships,Nucleophilicity,Organocatalysis},
   month = {7},
   pages = {584-595},
   title = {Do general nucleophilicity scales exist?},
   volume = {21},
   year = {2008},

    title = { Mayr's Database of Reactivity Parameters},
    url = {https://www.cup.lmu.de/oc/mayr/reaktionsdatenbank/},
    journal = {Database of Nucleophilicities and Electrophilicities},
    note = {accessed on 24/01/2023},
    urldate = {24/01/2023}

  • 1
    Welcome to TeX.SE. Please clarify the use case for your, shall we say, unusual desired labeling system for bibliographic entries. How is BibTeX to "know" that the sixth and seventh entries in the bib file are supposed to be labelled 6a and 6b rather than 6 and 7? E.g., will there be a field in the entries that tells BibTeX to switch from the standard labelling method (numeric, in the case of the rsc bibliography style) to a mixed numeric/alphabetical method?
    – Mico
    Jan 27, 2023 at 5:43
  • 1
    Incidentally, why doesn't the 7th entry contain author and year fields? It's quite clear that the author field should be author = {Herbert Mayr}... And why does the entry contain a journal field? The journal field makes sense only for entries of type @article. All other entry types, including @misc, simply ignore the journal field.
    – Mico
    Jan 27, 2023 at 5:51
  • 1
    Thank you Mico for your warm welcome. Basically, I am writing a Master's proposal and my supervisor is insisting to keep ref 6 and 7 together because ref 7 is a database made by Mayr and as far as I know he started to make the database from the work he has done in ref 6. I think it would be okay if I can get the numbering such that only \section{Scientific Approach/Methodology} can have mixed numeric/alphabetical method.
    – Nirajan KC
    Jan 27, 2023 at 10:05
  • The 7th entry is supposed to be a database entry. I didn't know @misc ignores the journal field, thank you for pointing it out. I will keep this in mind for the future. Is there a way to tell Tex to have mixed numeric/alphabetical method for certain section only?
    – Nirajan KC
    Jan 27, 2023 at 10:08
  • You ask, "Is there a way to tell Tex to have mixed numeric/alphabetical method for certain section only?" Not to my knowlege. A more general point: I think it's an extremely dubious practice to hijack one typographical convention -- e.g., how to write citation call-outs -- for an entirely seperate purpose -- say, to indicate that two particular publications are closely related because they were authored by the same person. If it's truly essential to point out that two publications are related so closely, you should so say explicitly, in words, in the body of the document.
    – Mico
    Jan 27, 2023 at 11:28


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