1. Introduction
Research is one of the most important processes in scientific societies, and one of the main stages and foundations of any research is the investigation of the Literature Review. Literature review has a special value and place in research, and the value of literature review increases when the researcher analyzes it critically, because stating the shortcomings and merits of past researches informs the researchers to find out in which field more research is needed and what are the deficiencies in research; this work shows the skill of the researcher and his mastery over the investigated researches. The literature review is not only a summary of previous researches, but the review of sources requires a complete and systematic analysis of the strengths, shortcomings and inaccuracies of past researches, and a careful review of the sources can guide the researcher in the field of research.

2. Literature Review
The results of the investigations show that, so far, inside and outside the country, no research has been done with a systematic review method with a critical analysis approach to collect sources on the topic of literature review; although Koreh-Paz (2016) has compared the literature review of two disciplines, a separate research, all the sources that have dealt with the issue of literature review in all disciplines have not been examined. Fatahi and Parirokh (1999), Karami (2017), Yahyavi (2015), Fit (2011), Nopf (2006), Winchester and Selji (2016) have taken steps to guide researchers in the field of literature review and also in research sources Hori (1997), Nariza et al (2014) have examined the year, topic relevance, sharing and quality of literature review.

3. Methodology
This research has collected studies and researches conducted in the field of literature review using a systematic review and a critical analysis approach, as well as a qualitative library-document method. In order to collect sources and select the appropriate source, the following steps were taken, which are as follows:
1- Determining the purpose of the research: according to the topic of the research, i.e. literature review and critical analysis of sources, all the researches and studies that were related to the topic of literature review were examined.
2- Searching for sources: in order to search for accurate sources related to the subject of research, considering that literature review is used in different disciplines and fields with different titles, first by checking in texts and books.
3- Analysis of sources: After searching the databases, a total of 64 sources were retrieved in Persian and non-Persian databases. By reviewing the sources, 13 sources had duplicate titles, which were removed from the collection of reviews, and then by reviewing the full text of the remaining sources, 20 articles were identified as unrelated to the research topic, although the titles of the sources show thematic relevance, in the review of the text, it was found that they are unrelated, because some sources have chosen literature review in the title of the word review, but within the text, especially in non-Persian sources, they have not paid attention to the issue of literature review. After going through the above steps, a total of 31 sources (articles, books and theses) were examined.
4- Extraction of thematic categories: after examining the full text of the selected sources, for its thematic classification, the most important topic that the source had examined from its own angle, the literature review, was placed as a category, meaning that the selected categories were extracted from the texts and based on the understanding and inference obtained from the sources, they were considered for this research, then according to the large number of categories extracted from the texts, categories were selected that had the highest frequency; in this way, the sources were divided into three categories, which are: 1- theoretical studies and guides (definition, importance, purpose and function) of literature review 2- evaluation criteria of literature review 3- criticality of literature review.

4. Results
The result indicates that the literature review is divided into 4 categories as follows:
1- Theoretical foundations and guidelines (definition, importance, purpose and function) of literature review:
 Most of the studies and researches that have been done in relation to the theoretical foundations of literature review are related to articles. The findings indicate that most of the studies intended to provide guidelines for the preparation of the literature review in addition to the importance and benefits of the literature review for researchers.
2- Reviewing the criticality of the literature review:
Table 2 shows that in the two studies that have been conducted in relation to critical analysis, although the basis of the research work was the critical analysis of the literature review, they did not criticize the sources as they should have, in the end, Korepaz's letter did not pay attention to the critical analysis of the literature review, and in the text of the literature review, he did not examine the literature with a critical approach, but besides this, Akindele's research examined the research with critical analysis, which he counted it as one of its merits.
3- Literature review evaluation criteria:
Most of the conducted researches have investigated the quality of the literature review, these researches take into consideration the criteria of the year, the structure of the literature review, the relevance of the topic, the impartiality of the researcher in the research work and information literacy education.

5. Discussion
Research is one of the important factors for the growth and success of societies, and researchers can be successful in conducting their research when they put the works and resources of the past at the forefront of their work. The review of the conducted researches and studies shows that most of the sources that have been written about the literature review have paid attention to the theoretical foundations of the literature review and it can be said that most of the researches have followed it. 

6. Conclusion
The results of the findings indicate that in the category of theoretical foundations, one of the strong points of the researches is that they have explained the importance, benefits and functions of the background of the research in an understandable and expressive manner. Also, one of the weaknesses of these studies is that they have not explained exactly how the researcher can compile a research background, and the guidelines of these studies are mostly theoretical and have not considered the practical development of the research background. In the category of critical review of backgrounds, one of the advantages of the researches is to pay attention to the review of the researches with a critical approach, but these researches have only addressed the weak points of the researches in the review of the sources and the research itself. Also, he did not critically analyze the sources he used. In the category of research background evaluation criteria, the most important criteria proposed in the researches for research background evaluation are: year, research background structure, subject relevance, researcher's impartiality in research work and information literacy education. Also, one of the strengths of the researches in this category is the provision of instructions, providing guidelines and considering criteria for evaluating the quality of the research backgrounds, and the weaknesses are the lack of clarity and understanding of the considered criteria.