(define-key ctl-x-4-map "r" 'find-file-read-only-other-window)
(define-key ctl-x-4-map "\C-f" 'find-file-other-window)
(define-key ctl-x-4-map "b" 'switch-to-buffer-other-window)
+(define-key ctl-x-4-map "o" 'display-buffer)
(define-key ctl-x-5-map "b" 'switch-to-buffer-other-screen)
(define-key ctl-x-5-map "f" 'find-file-other-screen)