Have you ever been to a movie without first reading reviews or asking your friends about it? Or, do you dine at a new place without being sanguine about the quality of food? Obviously no! Then how can you prepare your dissertation without confirming the reliability and relevance of the resources? Hence, one of the first steps of research process is carefully selecting the information sources that you are going to use. This applies to both primary and secondary sources. When selecting your primary sources, judge whether the participants are interested in the study and providing genuine information. You also have to qualify them to ensure that they are capable of answering your questions.
The secondary sources commonly used for research include journals, books, magazines, web sources, census reports, conference papers, etc. It is wrong to pick such references just to boost the number of entries in your bibliography, without a thorough consideration of their quality. You have to screen them on the basis of the following criteria:
• Relevance of matter: it is not sufficient for your references to be vaguely related to the subject that you are studying. They must be pertinent to the topic of research and provide some ideas or facts that are worth mentioning in the dissertation. They can either support your theory or refute it, but the logic or argument must be strong enough to be considered for research.
• Authenticity: check whether the author and publisher are completely authentic or not. The reference sources must not have any trace of plagiarism. Also ensure that the facts and figures given in the sources are 100% accurate. For this, you can double check them from any other source or talk to the author. Sometimes, the source of funding for publication also needs to be checked to ensure that the material is genuine and unbiased.
• Updated: ensure that the information provided in your references is up to date. Out dated facts and figures must not be made a part of the dissertation. Look for recent editions of books and journals.
Scrupulous scrutiny of references will take some time, but it will provide you a strong foundation for a valuable dissertation that is worthy of publication.
Dissertation Pal 
The information we collect for making our research complete should be appropriate for it and can give unique identity to the project. References collected by me helped me a lot as they helped me in deriving the research gap and later for my research.
The information collected from secondary sources should be reliable and authenticated and references should be up to date as it helps to determine source of information and gap for further studies