So we thought at that time that these aliens must have some way of materialising or 
(we; thought; T:at that time; that these aliens must have some way of materialising) Context(we thought,List([3, 13))):(these aliens; must have; some way of materialising)
we thought,List([3, 13))
we these aliens
thought must have
T:at that time that these aliens must have some way of materialising
some way of materialising