There are many resources to help you make a perfect bibliography. Print guides are at the circulation desk in the library but if you are typing your paper it may be easier to use one of these on-line bibliography tools. Those listed here are all free. Be sure your select the format your teacher wants (for example APA or MLA). If you are unable to locate all of the required information from a website your may want to consider using another source. Authoritative sites will provide this information. Authors who do not provide it may be writing with the purpose of swaying the audience, spreading misinformation or just stating their opinion without giving any reason to trust them as a source.