\"C-c o\" (a two-key sequence: the key `c' with the control modifier
followed by the key `o')
\"H-<left>\" (the cursor control key named \"left\" with the hyper modifier)
+ \"RET\" (the \"return\" key, also available as \"C-m\")
+ \"<return>\" (the \"<return>\" function key, which can be bound separately
+ from \"RET\" on some systems)
\"M-RET\" (the \"return\" key with a meta modifier)
\"C-M-<space>\" (the \"space\" key with both the control and meta modifiers)