The PostgreSQL 7.2.8 sources can be obtained by anonymous FTP from ftp://ftp.postgresql.org/pub/postgresql-7.2.8.tar.gz. Use a mirror if possible. After you have obtained the file, unpack it:
gunzip postgresql-7.2.8.tar.gz tar xf postgresql-7.2.8.tar
This will create a directory postgresql-7.2.8 under the current directory with the PostgreSQL sources. Change into that directory for the rest of the installation procedure.
If you see anything in the documentation that is not correct, does not match your experience with the particular feature or requires further clarification, please use this form to report a documentation issue.