This very much depends on the purpose of the literature review and where you are with your studies, e.g. undergraduate or Postgraduate. Your supervisor or tutor should specify a minimum number of references. Do remember to have at least 50% journal and book references and not depend totally on internet/web references.
The following are a general rule of thumb but do double check with your supervisor or lecturer:
A good literature review:
• clearly delimits the subject matter to be reviewed
• covers all important relevant literature
• is up-to-date
• provides an insightful analysis of the ideas and conclusions in the literature
• points out similarities and differences, strengths and weaknesses in the literature
• identifies gaps in the literature for future research
• identifies the context for which the literature is important.
The bibliography must always come at the end.
‘Literature’ covers everything relevant that is written on a topic: books, journal articles, newspaper articles, historical records, government reports, theses and dissertations, etc. The important word is 'relevant'. Check with your supervisor or tutor when in doubt. Please ensure quality of website/internet information.
The Literature review should consist of an introduction, body and conclusion.
In the introduction you should:
• define or identify the general topic, issue or area of concern
• point out overall trends in what has already been published
• establish your point of view for reviewing the literature
• indicate the organisation of the review.
In the body of the Review:
• group research studies and other relevant literature according to a common theme.
• summarise each item of literature appropriately according to its significance.
• compare and evaluate each item.
• provide topic sentences at the beginning of paragraphs and summary sentences at the end of sections to aid readers in their understanding of the main issues.
In the conclusion you should:
• summarise the literature maintaining the focus presented in the introduction
• evaluate the current "state of the art", pointing out gaps in the literature, inconsistencies and issues that are important for future study
• conclude by giving some insight into the relationship between your topic and a larger area of study or area of professional practice.
Start by making a list of keywords or subject headings that relate to the topic. Use your library. The library has experienced staff who can aid you in this search. Use the LibChat app on the main library page to speak directly to library staff for support.
Doing a literature review in health and social care : a practical guide by 
Doing a literature review in nursing, health and social care / Michael Coughlan, Patricia Cronin and Frances Ryan. by 