Release notes for prior release branches can be found on the PostgreSQL web site. At the time of release of version 11, these were the supported prior release branches:
      PostgreSQL 10:
      
       https://www.postgresql.org/docs/10/release.html
      
     
      PostgreSQL 9.6:
      
       https://www.postgresql.org/docs/9.6/release.html
      
     
      PostgreSQL 9.5:
      
       https://www.postgresql.org/docs/9.5/release.html
      
     
      PostgreSQL 9.4:
      
       https://www.postgresql.org/docs/9.4/release.html
      
     
      PostgreSQL 9.3:
      
       https://www.postgresql.org/docs/9.3/release.html
      
     
   Release notes for older release branches can be found at
   
    https://www.postgresql.org/docs/manuals/archive/