In several places the C-c a prefix is used as part of documenting a command. These key combos do not work unless C-c a has been set to org-agenda.
If you search the manual for "C-c a" you will not find "1.3 Activation" where it suggests configuring (global-set-key "\C-ca" 'org-agenda) Note the "missing" space. I suggest that places in the manual that use C-c a links to 1.3 (Introduction > Activation). -- Vagn Johansen