could concert
Regular verb: concert - concerted- concerted

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could concert
you could concert
she could concert
we could concert
you could concert
they could concert 	I could be concerting
you could be concerting
she could be concerting
we could be concerting
you could be concerting
they could be concerting	I could have concerted
you could have concerted
she could have concerted
we could have concerted
you could have concerted
they could have concerted	I could have been concerting
you could have been concerting
she could have been concerting
we could have been concerting
you could have been concerting
they could have been concerting	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't concert
you couldn't concert
she couldn't concert
we couldn't concert
you couldn't concert
they couldn't concert 	I couldn't be concerting
you couldn't be concerting
she couldn't be concerting
we couldn't be concerting
you couldn't be concerting
they couldn't be concerting	I couldn't have concerted
you couldn't have concerted
she couldn't have concerted
we couldn't have concerted
you couldn't have concerted
they couldn't have concerted	I couldn't have been concerting
you couldn't have been concerting
she couldn't have been concerting
we couldn't have been concerting
you couldn't have been concerting
they couldn't have been concerting	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I concert?
could you concert?
could she concert?
could we concert?
could you concert?
could they concert? 	could I be concerting?
could you be concerting?
could she be concerting?
could we be concerting?
could you be concerting?
could they be concerting? 	could I have concerted?
could you have concerted?
could she have concerted?
could we have concerted?
could you have concerted?
could they have concerted? 	could I have been concerting?
could you have been concerting?
could she have been concerting?
could we have been concerting?
could you have been concerting?
could they have been concerting? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I concert?
couldn't you concert?
couldn't she concert?
couldn't we concert?
couldn't you concert?
couldn't they concert? 	couldn't I be concerting?
couldn't you be concerting?
couldn't she be concerting?
couldn't we be concerting?
couldn't you be concerting?
couldn't they be concerting? 	couldn't I have concerted?
couldn't you have concerted?
couldn't she have concerted?
couldn't we have concerted?
couldn't you have concerted?
couldn't they have concerted? 	couldn't I have been concerting?
couldn't you have been concerting?
couldn't she have been concerting?
couldn't we have been concerting?
couldn't you have been concerting?
couldn't they have been concerting?