From: Structural and functional analysis of cellular networks with CellNetAnalyzer
==> rec3
==> rec2
==> rec1
!rec2 + rec1 ==> a
rec2 ==> b
rec3 ==> b
a ==> c
c + b ==> e
d ==> c
b ==> f
!c ==> d
f ==> tf3
d ==> tf1
e ==> tf2
tf3 ==>
tf2 ==>
tf1 ==>