If there are three or more authors of a work only the first author should be cited followed by et al. and the date
Example:
According to McDuff et al. (2017)....
OR
...(McDuff et al., 2017).
Last name, Initial(s)., Last name, Initial(s)., & Last name, Initial(s). (Year). Title (ed.). Publisher. DOI (if available)
Example:
McDuff, C., Smith, J., Kensington, K., Jones, S., Coughlan, S., Bortolin, L., Witte, M., Scott, A., Newport, A., Jensen, K., Wutzler, J., van Staden, I., McLean, J., Bergsma, G., Dowman, B., Petrie, K., Higgens, D., McCloud, R., Jessop, L. & Duncan, P. (2017). An introduction to quantitative analysis in finance. Houghton.
NB: In the reference list include all authors, however if a reference has 21 or more authors, the first 19 authors are listed followed by ... followed by the final author.