File psl-1983/3-1/doc/nmode/nm-subsystems.contents artifact 8a161d4abf part of check-in 9992369dd3

contents_entry(0 7 {Moving Up And Down Levels} 7-1)
contents_entry(1 7.1 {Subsystems} 7-1)
contents_entry(1 7.2 {Recursive Editing Levels} 7-1)
contents_entry(1 7.3 {Exiting Levels; Exiting NMODE} 7-2)