What do you understand by referencing and what are its different styles?

Decide on your area of research from the research papers provided ( Choose ONLY 3 of the attached papers) and find recent literature in this area.

•Write notes on critical review of literature.

•What do you understand by referencing and what are its different styles?

Attached papers on the link below:

https://drive.google.com/open?id=0B6B0NOs8_aynV3F0Nlg1UWdmYTA