There are several different ways to write references and reference lists (bibliographies). It all depends on which reference style you use.
To the right you can see the most commonly used styles and links to materials that show how they are used.
Those who want to publish an article in a scientific journal must follow the journal's instructions for how the references should look. These instructions tend to be found in "Author Instructions" on the journal website.
The Harvard style is an (author-year)-style. It consists of two parts, a reference in the text (the citation) and a bibliographic description in the reference list.
An author-year style similar to Harvard. The most visible difference is that the year is set out in brackets in the reference list. It is also praxis in APA not to include the page number in the in-text references (unless you quote).
MLA is also similar to the Harvard style. The big difference is that the year is not included in the in-text reference.
Vancouver system is a so-called number style. References in-text are indicated by numbers. The first source to appear in the text gets the number , the second source gets number  and so on. Each source keeps their numbers throughout the text. In the reference list, the sources listed in numerical order. The style has been developed by the International Committee of Medical Journal Editors.
IEEE style (Institute of Electrical and Electronics Engineers) is a style that is very similar to Vancouver. It is often used by engineers, particularly in computer and electrical engineering.
The Oxford style is a footnote style. In-text references use numbers to refer to a footnote at the bottom of each page, at the end of each chapter or at the end of the book.