It is absolutely essential that you acknowledge all the sources upon which your work relies. Failure to do so is likely to attract charges of plagiarism. Your department handbook sets out a detailed explanation of plagiarism and how to avoid it. I reproduce that explanation for your information, with some modifications to bring it into line with standard citation practices in language studies (as opposed to literary studies).
(From Department of English Handbook, 1998-1999, University of Birmingham: 25-27 - language studies related modifications indicated in the text in square brackets.)
Plagiarism: Its Cause and Cure
Plagiarism is a serious business: students have been expelled from the University or refused an honours degree on account of it. So it's worth spending some time on it. But what is it? And how can you be sure to avoid it?
A major objective of the English course (of any academic course, in fact) is to ensure that all students acquire the basic transferable skills in the pursuit of relevant information, its analysis and organisation and in the coherent presentation of arguments. It is not our objective to teach you simply to parrot information. We give out reading lists which we expect students to use in order to familiarise themselves with the nature of the debate on various subjects; but we don't expect these reading lists to be a substitute for the student's own input into the subject. You are expected to look at these texts critically: that is, to derive from them what is positive, and know that you have done so, and to develop or to argue with other things they may have to say, and to be conscious of the argument.
Two things come from this, the positive one of acknowledging where important ideas have come from, and the negative one of failing to acknowledge someone else's work, which is plagiarism. Plagiarism is simply passing off intellectual property as yours which is in fact someone else's. It is the most scorned academic sin, because it repre-sents intellectual laziness and dishonesty.
So, you must learn to quote and to provide references for your quotations. Anything that uses directly the words of some source must be indicated in inverted commas (or, with longer quotations, indented on a separate line) and a reference given, and the full reference of the book must be included in your bibliography at the end of your essay (You should include at the end of each piece you write a list of the books that you have used to help you write it. [short deletion]) Your reference is not only to acknowledge a debt but also to make sure that you and your reader can find the quotation again and examine its context, should it be particularly interesting (and if it isn't interesting, what have you quoted it for?) [Following paragraphs have been modified with reference to standard citation practices in linguistics.] If you use someone else's theories, suggestions, speculations, explanations, research findings, linguistic examples or evidence, basic pattern of argument or key terminology, you also need to acknowledge that you have done so. A properly referenced piece that is entering into dialogue with its sources should not have to worry about plagiarism but since you will be relying to such a considerable degree on the work of others, perhaps some exemplification will help.
Obviously if you were to directly quote or precisely paraphrase the words of another without acknowledgement and appropriate citation, this would be a case of unambiguous plagiarism and you should have no trouble avoiding such instances. But you must be equally scrupulous in acknowledging ideas, theories, formulations etc upon which you rely, or by which you have been influenced, even if you completely rework these in your own words. Consider the following.
