I could cite you could cite he could cite we could cite you could cite they could cite
V-ing form
I could be citing you could be citing he could be citing we could be citing you could be citing they could be citing
Perfect
I could have cited you could have cited he could have cited we could have cited you could have cited they could have cited
V-ing perfect
I could have been citing you could have been citing he could have been citing we could have been citing you could have been citing they could have been citing
Negation
Simple form
I couldn't cite you couldn't cite he couldn't cite we couldn't cite you couldn't cite they couldn't cite
V-ing form
I couldn't be citing you couldn't be citing he couldn't be citing we couldn't be citing you couldn't be citing they couldn't be citing
Perfect
I couldn't have cited you couldn't have cited he couldn't have cited we couldn't have cited you couldn't have cited they couldn't have cited
V-ing perfect
I couldn't have been citing you couldn't have been citing he couldn't have been citing we couldn't have been citing you couldn't have been citing they couldn't have been citing
Interrogative form
Simple form
could I cite? could you cite? could he cite? could we cite? could you cite? could they cite?
V-ing form
could I be citing? could you be citing? could he be citing? could we be citing? could you be citing? could they be citing?
Perfect
could I have cited? could you have cited? could he have cited? could we have cited? could you have cited? could they have cited?
V-ing perfect
could I have been citing? could you have been citing? could he have been citing? could we have been citing? could you have been citing? could they have been citing?
Interro-negative form
Simple form
couldn't I cite? couldn't you cite? couldn't he cite? couldn't we cite? couldn't you cite? couldn't they cite?
V-ing form
couldn't I be citing? couldn't you be citing? couldn't he be citing? couldn't we be citing? couldn't you be citing? couldn't they be citing?
Perfect
couldn't I have cited? couldn't you have cited? couldn't he have cited? couldn't we have cited? couldn't you have cited? couldn't they have cited?
V-ing perfect
couldn't I have been citing? couldn't you have been citing? couldn't he have been citing? couldn't we have been citing? couldn't you have been citing? couldn't they have been citing?