1. Google Scholar is a freely accessible web search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines.
2. Garda Rujukan Digital (GARUDA) formerly Portal Garuda Indonesian Publication Index by Institute of Advanced Engineering and Science Indonesia Section (IAES)
3.CrossRef is the publisher of the publisher's Digital Object Identifier (DOI)

4. Indonesia OneSearch (IOS) by National Library of Indonesia (Perpustakaan Nasional Republik Indonesia/Perpusnas)

5. JOURNAL FACTOR is a globally recognized forum for promoting your research work and knowledge sharing as we know research is all about communication.