When knitting the file as PDF it shows like this @Manual (which is the way i have typed it in the R markdown file)
This is what the bib file contains:
@Manual{anderson2015,
title = {Exhumation by debris flows in the 2013 Colorado Front Range storm},
author = { S.W. Anderson and S.P. Anderson and R.S Anderson},
journal = {Geology},
year = {2015},
pages = {31,94},
url = {https://www.R-project.org/},
}
In addition to writing your YAML as cderv says, you have to write the citations like this [@anderson2015] (i.e. the citation identifier from the bib file that corresponds to @Manual)