CrossRef - It is an Association of more than 1,400 publishers representing 4,000 societies and publishers including both commercial and non-profit organizations, its general purpose is to promote the development and cooperative use of new and innovative technologies to accelerate and facilitate academic research. provides the technical and business infrastructure to provide this reference link through digital object identifiers, it also provides the query service for DOI.
WorldCat - It is the most complete database of information on library collections in the world.OCLC delivers quality, relatability and value. Member libraries provide the foundation. Partners support WorldCat's growth.
Google Scholar o Google Academic (in Spanish) is the Google search engine specialized in academic documents. It was created in 2004 and is what you should use if you are a university student or are working on academic content.
ESJI - Unites in its database the most important scientific journals in Europe and Asia, which publishes the most authoritative and relevant research. The ESJI provides indexing of major international journals and proceedings. Author can get information about international journal impact factor, proceedings (research papers) and information on upcoming events. All the journal pages have pointers to Web pages of the publishers which are integrated into the ESJI stream pages.
Scilit - It is a free, comprehensive database for scientists that uses a new method of collecting data and indexing scientific material. Our crawlers pull the latest data from CrossRef and PubMed daily. This means that newly published articles are added to Scilit immediately.
Citefactor - Is a service that provides access to quality controlled Open Access Journals. The Directory indexing of journal aims to be comprehensive and cover all open access scientific and scholarly journals that use an appropriate quality control system, and it will not be limited to particular languages or subject areas. The aim of the Directory is to increase the visibility and ease of use of open access scientific and scholarly journals thereby promoting their increased usage and impact.
ResearchBib - Is open access with high standard indexing database for researchers and publishers. Research Bible may freely index journals, research papers, call for papers, research position.
DRJI - Provides immediate access to educational literature to support the use of educational research and information to improve practice in learning, teaching, educational decision-making and research.
Index Copernicus - It is an online database of user-contributed information, including profiles of scientists, as well as scientific institutions, publications and projects established in 1999 in Poland and managed by Index Copernicus International.
BASE - Is one of the world's most voluminous search engines especially for academic web resources. BASE provides more than 300 million documents from more than 10,000 content providers. You can access the full texts of about 60% of the indexed documents for free (Open Access). BASE is operated by Bielefeld University Library.