New developer interested in including the BV parameter for diodes

I am interested in helping this project because I am impressed at what
it can do. This is my first attempt at developing for any type of open
source project so bear with me.

I was looking at the diodes and noticed that the BV parameter
(Breakdown Voltage) is ignored. This makes modeling a zener diode very
awkward. Is there a specific reason the parameter is ignored? I saw a
section under a couple of the models that look like that parameter
will be added in the future, is something in there already?

If it is not in there for a good reason, I would like to attempt to
add it. I looked at the source code under the diode section, and there
were different models, some that I would rather look up more
information before I putz with them. When I am trying to stand on the
shoulders of giants, I would like to know what the giants have done
before I dive in. Is there any good websites or books with the models
that are used in gnucap?