could overstudy
Regular verb: overstudy - overstudied- overstudied

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could overstudy
you could overstudy
he could overstudy
we could overstudy
you could overstudy
they could overstudy 	I could be overstudying
you could be overstudying
he could be overstudying
we could be overstudying
you could be overstudying
they could be overstudying	I could have overstudied
you could have overstudied
he could have overstudied
we could have overstudied
you could have overstudied
they could have overstudied	I could have been overstudying
you could have been overstudying
he could have been overstudying
we could have been overstudying
you could have been overstudying
they could have been overstudying	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't overstudy
you couldn't overstudy
he couldn't overstudy
we couldn't overstudy
you couldn't overstudy
they couldn't overstudy 	I couldn't be overstudying
you couldn't be overstudying
he couldn't be overstudying
we couldn't be overstudying
you couldn't be overstudying
they couldn't be overstudying	I couldn't have overstudied
you couldn't have overstudied
he couldn't have overstudied
we couldn't have overstudied
you couldn't have overstudied
they couldn't have overstudied	I couldn't have been overstudying
you couldn't have been overstudying
he couldn't have been overstudying
we couldn't have been overstudying
you couldn't have been overstudying
they couldn't have been overstudying	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I overstudy?
could you overstudy?
could he overstudy?
could we overstudy?
could you overstudy?
could they overstudy? 	could I be overstudying?
could you be overstudying?
could he be overstudying?
could we be overstudying?
could you be overstudying?
could they be overstudying? 	could I have overstudied?
could you have overstudied?
could he have overstudied?
could we have overstudied?
could you have overstudied?
could they have overstudied? 	could I have been overstudying?
could you have been overstudying?
could he have been overstudying?
could we have been overstudying?
could you have been overstudying?
could they have been overstudying? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I overstudy?
couldn't you overstudy?
couldn't he overstudy?
couldn't we overstudy?
couldn't you overstudy?
couldn't they overstudy? 	couldn't I be overstudying?
couldn't you be overstudying?
couldn't he be overstudying?
couldn't we be overstudying?
couldn't you be overstudying?
couldn't they be overstudying? 	couldn't I have overstudied?
couldn't you have overstudied?
couldn't he have overstudied?
couldn't we have overstudied?
couldn't you have overstudied?
couldn't they have overstudied? 	couldn't I have been overstudying?
couldn't you have been overstudying?
couldn't he have been overstudying?
couldn't we have been overstudying?
couldn't you have been overstudying?
couldn't they have been overstudying?