Def [e, e'] == filter(ev.es-ble{i:l}(es;e;ev);before(e') @ [e'])

is mentioned by

Thm* es:ES, e,e',ev:E. (ev  [e, e'])  e  ev  & ev  e'

[member-es-interval]

Try larger context: EventSystems IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html