The bibliography file
The bibliography file is kept at bibliography/biblio.bib -- a bibtex file. The bibtex file can be filled in from any source and if you work with markdown, then use Latex citation style to cite the sources. Authorea will adjust the citation and the references. Anyone can fill in the bibtex file with entries and anyone who has access to this file who can edit it can draw on the content of the bibtex file to add citations and shape up the reference list as one wishes. There is nothing to configure in the bibtex file beyond just adding citations. At different point one can add and modify citations or a group of authors can add/edit citations.
The layout file