I usually get my specs from
etsi.org directly. Updates get published all the
time, sometimes fixing bugs, and it's a bad idea to be stuck on an older
version. They also have a search that has more than once helped me to find the
relevant spec number for a gem that I had forgotten where to find:
https://www.etsi.org/
The catch is that on the top search bar, first click on "Standards", then
search. That will get you to a more extensive search filter.
Interestingly enough, I can't find 44.007 there at all. Are you sure that
number is correct? So far I have found everything else without a problem.
For LCLS, I find 23.284
https://www.etsi.org/deliver/etsi_ts/123200_123299/123284/15.00.00_60/ts_12…
~N