Dictionaries and encyclopaedias are helpful places to start your research, as they define & clarify concepts and terminology. Good encyclopaedias will usefully summarise a topic, and many offer suggestions for further reading.
Rather than use free Web sources (which are often unreliable), you could use the range of reference books at HB 61 on floor 3. The New Palgrave Dictionary of Economics has excellent articles, and is also available online (and regularly updated):
Open access dictionaries that may be of limited use:
For the social sciences more broadly, consult this excellent resource:
International Encyclopedia of the Social & Behavioral Sciences. 2nd ed. (Elsevier: 2015)
Handbooks are useful for summarising the state of research across a topic (and its subdivisions) at the time of publication. They help to give an idea of the main areas of research, themes & debates, the leading researchers, as well as useful references you can follow up. Academic publishers like Oxford University Press, Routledge, and Edward Elgar publish good handbooks (see catalogue for details), and the Library subscribes to the highly regarded series Handbooks in Economics, published by Elsevier. These are available on the ScienceDirect database: