must refer
Verbo regular: refer - referred- referred

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must refer
you must refer
she must refer
we must refer
you must refer
they must refer 	I must be referring
you must be referring
she must be referring
we must be referring
you must be referring
they must be referring	I must have referred
you must have referred
she must have referred
we must have referred
you must have referred
they must have referred	I must have been referring
you must have been referring
she must have been referring
we must have been referring
you must have been referring
they must have been referring	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must not refer
you must not refer
she must not refer
we must not refer
you must not refer
they must not refer 	I must not be referring
you must not be referring
she must not be referring
we must not be referring
you must not be referring
they must not be referring	I must not have referred
you must not have referred
she must not have referred
we must not have referred
you must not have referred
they must not have referred	I must not have been referring
you must not have been referring
she must not have been referring
we must not have been referring
you must not have been referring
they must not have been referring	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I refer?
must you refer?
must she refer?
must we refer?
must you refer?
must they refer? 	must I be referring?
must you be referring?
must she be referring?
must we be referring?
must you be referring?
must they be referring? 	must I have referred?
must you have referred?
must she have referred?
must we have referred?
must you have referred?
must they have referred? 	must I have been referring?
must you have been referring?
must she have been referring?
must we have been referring?
must you have been referring?
must they have been referring? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I not refer?
must you not refer?
must she not refer?
must we not refer?
must you not refer?
must they not refer? 	must I not be referring?
must you not be referring?
must she not be referring?
must we not be referring?
must you not be referring?
must they not be referring? 	must I not have referred?
must you not have referred?
must she not have referred?
must we not have referred?
must you not have referred?
must they not have referred? 	must I not have been referring?
must you not have been referring?
must she not have been referring?
must we not have been referring?
must you not have been referring?
must they not have been referring?