Vancouver style is usually used for science and medical journals and was developed in Vancouver and has existed since 1978.
The Chicago Manual of Style (CMOS) is a style guide for American English published since 1906 by the University of Chicago Press. Its seventeen editions have prescribed writing and citation styles widely used in publishing.
There are several different ways to cite a source in academic writing. In the past, every subject and specialty has had its own rule for referencing, but today there is a greater tendency among universities and colleges to choose a common method.