Web services composition is one of the most fundamental and pressing issues when developing Web-based systems in accordance with Service-Oriented Architecture. The main challenge is selecting and composing a proper set of web services to fulfil various demands of clients over the World-Wide-Web. This paper reports results of a systematic literature review conducted on the state of the art of achievements in web services composition. It starts with a set of research questions that lead to a set of relevant keywords for querying four well-known digital libraries. Search results are then filtered through based on some inclusion and exclusion criteria. Finally, 269 most relevant documents were identified. The extracted information from these resources is analysed and results are reported, concerning three major viewpoints: bibliography, research quality, and strategy.