is mentioned by

Thm* a,tr,P:Top. [a / tr] | P ~ if P(kind(a)) [a / tr | P] else tr | P fi	[trace_projection_cons]
Thm* P:Top. nil | P ~ nil	[trace_projection_nil]
Thm* d:Decl, t1,t2:(d) List, P:(Label). t1 @ t2 | P ~ (t1 | P @ t2 | P)	[trace_projection_append]

Try larger context: GenAutomata