You would use italics to punctuate the title of a(n)

book

poem

article

speech

failure to properly credit the sources of your information is an act of

credibility

plagiarism

validity

logos

In general, we use italics to highlight the title of texts that can stand by themselves, which means that you can italicize in the text the title of a book, but it can be used also for a title of a poem, article or maybe significant speech. In the bibliography we use italics for a book title (a novel, book of poetry or essays, research report, etc.). 
Not including source of information used in a paper is a plagiarism. Each source of information used in a paper (paraphrased or quoted) should be mentioned. In a paper you can use different citation styles, e.g. APA, MLA or Chicago style, but in all cases, all quoted or used sources of information need to be listed in the works citied page (bibliography).