Mendeley is a free reference manager and an academic social network. You can create your personal account in Mendeley directly from the website. You can use your personal e-mail address to register.
As a second step, download the Desktop version either for Windows, MAC OS and Linux and to get the Web Importer/Citation Plugin tools to further enhance your research.
Zotero is a free and open-source reference management software to manage bibliographic data and related research materials. You can freely download, install, and use it directly from the website.
Wizdom.ai (formerly Colwiz) is a free and comprehensive research management software for researchers, academics and students. With the wizdom.ai android app, you can search, add and manage publications in your wizdom.ai library on the go.