must overwinter
Regular verb: overwinter - overwintered- overwintered

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must overwinter
you must overwinter
he must overwinter
we must overwinter
you must overwinter
they must overwinter 	I must be overwintering
you must be overwintering
he must be overwintering
we must be overwintering
you must be overwintering
they must be overwintering	I must have overwintered
you must have overwintered
he must have overwintered
we must have overwintered
you must have overwintered
they must have overwintered	I must have been overwintering
you must have been overwintering
he must have been overwintering
we must have been overwintering
you must have been overwintering
they must have been overwintering	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't overwinter
you mustn't overwinter
he mustn't overwinter
we mustn't overwinter
you mustn't overwinter
they mustn't overwinter 	I mustn't be overwintering
you mustn't be overwintering
he mustn't be overwintering
we mustn't be overwintering
you mustn't be overwintering
they mustn't be overwintering	I mustn't have overwintered
you mustn't have overwintered
he mustn't have overwintered
we mustn't have overwintered
you mustn't have overwintered
they mustn't have overwintered	I mustn't have been overwintering
you mustn't have been overwintering
he mustn't have been overwintering
we mustn't have been overwintering
you mustn't have been overwintering
they mustn't have been overwintering	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I overwinter?
must you overwinter?
must he overwinter?
must we overwinter?
must you overwinter?
must they overwinter? 	must I be overwintering?
must you be overwintering?
must he be overwintering?
must we be overwintering?
must you be overwintering?
must they be overwintering? 	must I have overwintered?
must you have overwintered?
must he have overwintered?
must we have overwintered?
must you have overwintered?
must they have overwintered? 	must I have been overwintering?
must you have been overwintering?
must he have been overwintering?
must we have been overwintering?
must you have been overwintering?
must they have been overwintering? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I overwinter?
mustn't you overwinter?
mustn't he overwinter?
mustn't we overwinter?
mustn't you overwinter?
mustn't they overwinter? 	mustn't I be overwintering?
mustn't you be overwintering?
mustn't he be overwintering?
mustn't we be overwintering?
mustn't you be overwintering?
mustn't they be overwintering? 	mustn't I have overwintered?
mustn't you have overwintered?
mustn't he have overwintered?
mustn't we have overwintered?
mustn't you have overwintered?
mustn't they have overwintered? 	mustn't I have been overwintering?
mustn't you have been overwintering?
mustn't he have been overwintering?
mustn't we have been overwintering?
mustn't you have been overwintering?
mustn't they have been overwintering?