I could thumb-index you could thumb-index he could thumb-index we could thumb-index you could thumb-index they could thumb-index
V-ing form
I could be thumb-indexing you could be thumb-indexing he could be thumb-indexing we could be thumb-indexing you could be thumb-indexing they could be thumb-indexing
Perfect
I could have thumb-indexed you could have thumb-indexed he could have thumb-indexed we could have thumb-indexed you could have thumb-indexed they could have thumb-indexed
V-ing perfect
I could have been thumb-indexing you could have been thumb-indexing he could have been thumb-indexing we could have been thumb-indexing you could have been thumb-indexing they could have been thumb-indexing
Negation
Simple form
I could not thumb-index you could not thumb-index he could not thumb-index we could not thumb-index you could not thumb-index they could not thumb-index
V-ing form
I could not be thumb-indexing you could not be thumb-indexing he could not be thumb-indexing we could not be thumb-indexing you could not be thumb-indexing they could not be thumb-indexing
Perfect
I could not have thumb-indexed you could not have thumb-indexed he could not have thumb-indexed we could not have thumb-indexed you could not have thumb-indexed they could not have thumb-indexed
V-ing perfect
I could not have been thumb-indexing you could not have been thumb-indexing he could not have been thumb-indexing we could not have been thumb-indexing you could not have been thumb-indexing they could not have been thumb-indexing
Interrogative form
Simple form
could I thumb-index? could you thumb-index? could he thumb-index? could we thumb-index? could you thumb-index? could they thumb-index?
V-ing form
could I be thumb-indexing? could you be thumb-indexing? could he be thumb-indexing? could we be thumb-indexing? could you be thumb-indexing? could they be thumb-indexing?
Perfect
could I have thumb-indexed? could you have thumb-indexed? could he have thumb-indexed? could we have thumb-indexed? could you have thumb-indexed? could they have thumb-indexed?
V-ing perfect
could I have been thumb-indexing? could you have been thumb-indexing? could he have been thumb-indexing? could we have been thumb-indexing? could you have been thumb-indexing? could they have been thumb-indexing?
Interro-negative form
Simple form
could I not thumb-index? could you not thumb-index? could he not thumb-index? could we not thumb-index? could you not thumb-index? could they not thumb-index?
V-ing form
could I not be thumb-indexing? could you not be thumb-indexing? could he not be thumb-indexing? could we not be thumb-indexing? could you not be thumb-indexing? could they not be thumb-indexing?
Perfect
could I not have thumb-indexed? could you not have thumb-indexed? could he not have thumb-indexed? could we not have thumb-indexed? could you not have thumb-indexed? could they not have thumb-indexed?
V-ing perfect
could I not have been thumb-indexing? could you not have been thumb-indexing? could he not have been thumb-indexing? could we not have been thumb-indexing? could you not have been thumb-indexing? could they not have been thumb-indexing?