The majority of Q2DP documents is written in SGML.
If you are not familiar with SGML, you should take the ASCII plain text version and simply rewrite the section you want to extend or correct. The best way to to get the plain text version is the Q2DParchive.
Please make sure to list the full (sub)section title - the numbers are dynamically generated and not in the SGML, and might have changed.