must concern
Regular verb: concern - concerned- concerned

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must concern
you must concern
he must concern
we must concern
you must concern
they must concern 	I must be concerning
you must be concerning
he must be concerning
we must be concerning
you must be concerning
they must be concerning	I must have concerned
you must have concerned
he must have concerned
we must have concerned
you must have concerned
they must have concerned	I must have been concerning
you must have been concerning
he must have been concerning
we must have been concerning
you must have been concerning
they must have been concerning	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't concern
you mustn't concern
he mustn't concern
we mustn't concern
you mustn't concern
they mustn't concern 	I mustn't be concerning
you mustn't be concerning
he mustn't be concerning
we mustn't be concerning
you mustn't be concerning
they mustn't be concerning	I mustn't have concerned
you mustn't have concerned
he mustn't have concerned
we mustn't have concerned
you mustn't have concerned
they mustn't have concerned	I mustn't have been concerning
you mustn't have been concerning
he mustn't have been concerning
we mustn't have been concerning
you mustn't have been concerning
they mustn't have been concerning	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I concern?
must you concern?
must he concern?
must we concern?
must you concern?
must they concern? 	must I be concerning?
must you be concerning?
must he be concerning?
must we be concerning?
must you be concerning?
must they be concerning? 	must I have concerned?
must you have concerned?
must he have concerned?
must we have concerned?
must you have concerned?
must they have concerned? 	must I have been concerning?
must you have been concerning?
must he have been concerning?
must we have been concerning?
must you have been concerning?
must they have been concerning? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I concern?
mustn't you concern?
mustn't he concern?
mustn't we concern?
mustn't you concern?
mustn't they concern? 	mustn't I be concerning?
mustn't you be concerning?
mustn't he be concerning?
mustn't we be concerning?
mustn't you be concerning?
mustn't they be concerning? 	mustn't I have concerned?
mustn't you have concerned?
mustn't he have concerned?
mustn't we have concerned?
mustn't you have concerned?
mustn't they have concerned? 	mustn't I have been concerning?
mustn't you have been concerning?
mustn't he have been concerning?
mustn't we have been concerning?
mustn't you have been concerning?
mustn't they have been concerning?