To be made up of:
If accessed on the internet, add:
(Duncan and Trejo, 2011).
Duncan, B. and Trejo, S. J. (2011). Low-skilled immigrants and the U.S. labor market. IZA Discussion Paper no. 5964. Bonn: Institute for the Study of Labor. Available at https://ftp.iza.org/dp5964.pdf (Accessed: 3 March 2016).