Papers about Cadabra
The canonical introduction to Cadabra for high-energy physicists is the original paper (now updated for 2.x syntax),
hep-th/0701238 (now updated for 2.x syntax)
The Cadabra 2.x software is published as
Cadabra2: computer algebra for field theory revisited
Please cite the two papers above when you use Cadabra in your own work; those citations are the only way to convince the bean counters that this software is useful.
A general introduction to Cadabra (the old version, that is) can be found in
A technical explanation of the motivation for writing this software, as well as a sketch of the internal structure, can be found in the paper
A paper describing the new features of version 2 is in preparation and will appear sometime in 2019.
Leo Brewin has written a nice introduction to Cadabra version 1 for people who intend to use it in General Relativity,
also available as arxiv:0903.2085
Research papers citing Cadabra
The list of papers citing cadabra is getting too long to maintain by hand, but Google Scholar does an excellent job at it. See the list of papers citing the Comp.Phys.Comm. paper and the list of papers citing the hep-th paper.