Discuss, with examples, four commonly used citation and referencing styles.

1. APA (American Psychological Association) Style:
APA style is commonly used in the social sciences, such as psychology, sociology, and education. In-text citations in APA style include the author's last name and the year of publication (Smith, 2019). The reference list at the end of the paper includes full bibliographic information for each source cited, arranged alphabetically by author's last name. For example, a book citation in APA style would look like this: Smith, J. (2019). The Art of Writing. New York: Publisher.

2. MLA (Modern Language Association) Style:
MLA style is often used in the humanities, such as literature, language, and cultural studies. In-text citations in MLA style include the author's last name and the page number (Smith 45). The Works Cited page at the end of the paper lists full bibliographic information for each source cited, arranged alphabetically by author's last name. For example, a journal article citation in MLA style would look like this: Smith, John. "The Impact of Technology on Education." Journal of Education, vol. 25, no. 2, 2018, pp. 45-60.

3. Chicago Style:
Chicago style is commonly used in history, art history, and some social sciences. There are two variations of Chicago style: notes and bibliography and author-date. In the notes and bibliography style, footnotes or endnotes are used for in-text citations, and a bibliography is included at the end of the paper. In the author-date style, in-text citations include the author's last name and the year of publication, similar to APA style. For example, a book citation in Chicago style would look like this: Smith, John. The Art of Writing. New York: Publisher, 2019.

4. Harvard Style:
Harvard style is a generic author-date citation style that is commonly used in various disciplines. In-text citations in Harvard style include the author's last name and the year of publication (Smith 2019). The reference list at the end of the paper includes full bibliographic information for each source cited, arranged alphabetically by author's last name. For example, a website citation in Harvard style would look like this: Smith, J. (2019). "The Importance of Proper Citation." Retrieved from www.example.com.

1. American Psychological Association (APA)

- In-text citation: (Author, Year)
- Example: (Smith, 2023)

- Reference list entry:
```
Smith, J. (2023). The benefits of exercise. Journal of Health Psychology, 28(1), 1-10.
```

2. Modern Language Association (MLA)

- In-text citation: (Author Page Number)
- Example: (Smith 10)

- Works cited entry:
```
Smith, John. "The Benefits of Exercise." Journal of Health Psychology, vol. 28, no. 1, 2023, pp. 1-10.
```

3. Chicago Manual of Style (CMS)

- In-text citation: (Author, Year, Page Number)
- Example: (Smith 2023, 10)

- Bibliography entry:
```
Smith, John. The Benefits of Exercise. Journal of Health Psychology 28, no. 1 (2023): 1-10.
```

4. IEEE

- In-text citation: [Number]
- Example: [1]

- Reference list entry:
```
[1] J. Smith, "The benefits of exercise," Journal of Health Psychology, vol. 28, no. 1, pp. 1-10, 2023.
```