I am writting my thesis in seperate chapters that I want to combine into one final document, how can I have the references at the end of the master document without duplicates rather than at the end of each chapter ?
First, make backup copies of your chapter files - which is always good practice when working with important materials.
Then with one set of your chapter files, unformat the citations in each chapter which will replace the in-text citations with temporary citations (curly brackets). Next, append each chapter to create one document. Once the document (encompassing all the chapters) is completed, format the citations to replace the temporary citations and generate a complete bibliography.