(Burkhardt and Morris 410). : A typical reference for one or two authors.
(Crowne). : The reference comes from a web document without pagination.
("Singular and Plural” 16). : Journal article without author from an online database. The URL is given as the article does not have a DOI.
Esposito et al. ...... (45-46). : The book has more than two authors who are mentioned in the text and only the page numbers are included in the brackets.
You may also like to look at the example papers provided on the MLA Style Centre