This paper provides an in-depth review of the literature on citation impact indicators, which are used to evaluate the scientific impact of publications and research units. The review covers various aspects, including the selection of publications and citations, normalization, counting methods for co-authored publications, and citation impact indicators for journals. The literature on bibliographic databases such as Web of Science, Scopus, and Google Scholar is also reviewed, focusing on their coverage and limitations. The paper concludes with recommendations for future research, emphasizing the need for more comprehensive and accurate citation impact indicators.This paper provides an in-depth review of the literature on citation impact indicators, which are used to evaluate the scientific impact of publications and research units. The review covers various aspects, including the selection of publications and citations, normalization, counting methods for co-authored publications, and citation impact indicators for journals. The literature on bibliographic databases such as Web of Science, Scopus, and Google Scholar is also reviewed, focusing on their coverage and limitations. The paper concludes with recommendations for future research, emphasizing the need for more comprehensive and accurate citation impact indicators.