Vancouver
This is the Vancouver style for referencing, used at the Univerity of Portsmouth within the School of Pharmacy and Biomedical Sciences and the Radiography departments.
This guide is modelled on Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers (2nd edition). You may wish to consult this source directly for additional information or examples.
You must reference anything you use which is not your own work in order to avoid being accused of plagiarism.
Having said this, you will find that many departments at Portsmouth do not allow you to use lecture notes as the source for your essays. You should use the reading list which your lecturer has given you and turn to those sources when writing your essay. If your lecturer has not indicated where they got their information, and you want to use it, go and ask for the source.