(Autor, year) reference as well as citation style

Question

The journal publisher has certain demands for citation and references which I have to fulfill. Following are the demands:

All citations in text should refer to: 1. Upto two authors: Both authors last name without initials {comma} year of publication. 2. More than two authors: First author's last name followed by et al. {comma} year of publication.

All references: References should be sorted alphabetically and then chronologically. More than one reference from the same author(s) in the same year must be identified by the letters 'a', 'b', 'c' etc. placed after the year of publication.

Examples:

Reference to a journal publication: Van der Geer, J., Hanraads, J.A.J., Lupton, R.A., 2010. The art of writing a scientific article. J. Sci. Commun. 163, 51–59.

Reference to a book: Strunk Jr., W., White, E.B., 2000. The Elements of Style, fourth ed. Longman, New York.

My efforts:

I tried to use biblatex for the first time since I read that it has more options for customization. I keep getting errors of the form

command ---- already defined

for commands \bibhand, \c@author, \citename, \bibfont, \Citeauthor

I investigated the .cls file and found that it uses natbib package by including the line: \RequirePackage[\@biboptions]{natbib}. I tried with natbib package by including the following line:

\usepackage[square,sort,comma,numbers]{natbib}

It gave me an error, Option clash for package natbib. I have no clue what else to do. Could somebody guide me as to how I should generate the required reference and citation styles?

Note: I would preferably not change the .cls file since it is provided by publishers, but I can try out such solutions. The source for above text is: http://www.elsevier.com/journals/medical-image-analysis/1361-8415/guide-for-authors#68000

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Update: I commented out the line in .cls file which loads natbib. Now problem with natbib is solved. I am trying to get desired results with natbib

Answer 1

Since it looks like you're using the document class elsarticle (which, as you've discovered, already loads the natbib package), you may want to execute the following command:

\biboptions{square,sort,comma,numbers}

This method is described in more detail on pages 2 and 3 of the user guide of the elsarticle package.

The elsarticle package comes with three separate bibliography style files: elsarticle-num.bst, elsarticle-num-names.bst, and elsarticle-harv.bst. The first or second of these should give you the formatting you require. (elsarticle-harv, in contrast, is meant for authoryear-style citation callouts, which doesn't seem to be what you want.)

Note that if authoryear was meant to be one of the options passed to natbib, one would have to specify it as an option to the document class:

\documentclass[authoryear{,<other options>}]{elsarticle}

Answer 2

The option clash comes from the fact that your class file loads natbib without options, and you load it with some options. You should not load it, and give the options to the document class; the class will hand the options on to natbib.

Btw, biblatex has a natbib emulation mode. Probably loading biblatex with option natbib=true would suppress the error messages (not sure, though).