I could concertise you could concertise he could concertise we could concertise you could concertise they could concertise
V-ing form
I could be concertising you could be concertising he could be concertising we could be concertising you could be concertising they could be concertising
Perfect
I could have concertised you could have concertised he could have concertised we could have concertised you could have concertised they could have concertised
V-ing perfect
I could have been concertising you could have been concertising he could have been concertising we could have been concertising you could have been concertising they could have been concertising
Negation
Simple form
I could not concertise you could not concertise he could not concertise we could not concertise you could not concertise they could not concertise
V-ing form
I could not be concertising you could not be concertising he could not be concertising we could not be concertising you could not be concertising they could not be concertising
Perfect
I could not have concertised you could not have concertised he could not have concertised we could not have concertised you could not have concertised they could not have concertised
V-ing perfect
I could not have been concertising you could not have been concertising he could not have been concertising we could not have been concertising you could not have been concertising they could not have been concertising
Interrogative form
Simple form
could I concertise? could you concertise? could he concertise? could we concertise? could you concertise? could they concertise?
V-ing form
could I be concertising? could you be concertising? could he be concertising? could we be concertising? could you be concertising? could they be concertising?
Perfect
could I have concertised? could you have concertised? could he have concertised? could we have concertised? could you have concertised? could they have concertised?
V-ing perfect
could I have been concertising? could you have been concertising? could he have been concertising? could we have been concertising? could you have been concertising? could they have been concertising?
Interro-negative form
Simple form
could I not concertise? could you not concertise? could he not concertise? could we not concertise? could you not concertise? could they not concertise?
V-ing form
could I not be concertising? could you not be concertising? could he not be concertising? could we not be concertising? could you not be concertising? could they not be concertising?
Perfect
could I not have concertised? could you not have concertised? could he not have concertised? could we not have concertised? could you not have concertised? could they not have concertised?
V-ing perfect
could I not have been concertising? could you not have been concertising? could he not have been concertising? could we not have been concertising? could you not have been concertising? could they not have been concertising?