This seems to be Citation-Name system (C-N system) or the Alpha-numeric method, one of the three styles recommended by the Council of Science Editors (CSE). In this system, the end references are listed alphabetically by the surnames of authors and numbered consecutively. For example, if the authors are Bhatt, Chatterjee, Abu, Abraham, Aditya, and Menon, the first entry authored by Abu would get the number 1, Abraham, number 2, Aditya, number 3, Bhatt, number 4, Chatterjee, number 5, Menon, number 6, and so on. If you are doing it manually, you may rearrange file cards in alphabetical order by the surnames of the first authors and numbered. Those numbers must then be inserted in the text as superscript.

The numbers assigned to the end references would be used for in-text citations irrespective of the sequence in which they appear in the text. For example, if a work by Menon were number 6 in the reference list, each in-text citation to Menon would get the number 6.

Dear C George,

Your answer was so helpful, I got it and it worked perfectly. There are different ways even within CSE, but the " numerical superscript, alphabetically sorted" option was the one I was in a desperate need.

There are several referencing styles such as alphabetical (Harvard), numeric (Vancouver), and alphanumeric, each of which has advantage and disadvantage. Of these, Survey of Ophthalmology appears to require the alphanumeric style with plug-ins provided ( https://open.mendeley.com/use-citation-style/survey-of-ophthalmology ), although its author instruction also says the Vancouver style for formatting references ( https://www.surveyophthalmol.com/content/authorinfo ).

Dear Nobuyuki,

Thanks for your suggestions. From the beginning, alpha-numeric style of referencing (numerical superscript, alphabetically sorted) was strange to me. I used paperpile plug-in, which works well in google drive document, and it really has different options for referencing. Ya, the journal's instruction is misleading; it says use Vancouver referencing style, however, you don't find the numerical superscript style, sorted alphabetically (based on author's name). But, the suggestion from C George was helpful; I used the CSE referencing style, which matches with the journal's requirement.

HI can any1 help?The citations which i put using mendeley.Now the numbering of my referrences are not alphabetcically arranged,But if i arrange it alphabetically,then my numbering in text changes?wat to do now.An the journal wants it to be arranged alphabetically.