How to group multiple references with a single number in the text?

I am writing a report for an organization that wants references grouped, so if you have three references for a particular sentence the period will be followed by a single arabic numeral (1). All of the cited references woudl be listed under the number (1) in the bibiliography.

I tried going to output styles → edit my style → numbering → grouped references → use one number for references always cited together

But this does not give me a single arabic number. Also, to add to confusion, the foundation would like if a reference is repeated that it get that original number. 

Could you suggest how I might format this? Thank you!

Which output style file are you using? Presumably it’s a numbered style – to group citations you need to modify* the citations “Numbering” setting to include “Use one number for references cited together”. (Refer to the attached image.)

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*Go to the Endnote toolbar and select Edit >Output Styles > Edit [name of your output style]. In the output style’s dialog box locate the Citations section and click to select “Numbering”. In the right section of the dialog box check the box for “Use one number for references cited together”. Exit the.box which will save the change to a new style file having the word “Copy” added to the name. Change the MS Word setting to use the new output style.

output style_citations-numbering.gif