Thank you Harshvardhan

Dear Sujit,

For scale development process, there are few good references suggesting process and related sample size. Here is one

1) For Pre-testing of Questionnaire

Zikmund, W. G. (2003). Sample designs and sampling procedures. Business research methods, 7, 368-400.

2) Clark, L. A., & Watson, D. (1995). Constructing validity: Basic issues in objective scale development. Psychological assessment, 7(3), 309.

This has over 3000 citation and very informative.

Hope this will help you. 

Regards,

Gobinda