must sum
Verbo regular: sum - summed- summed

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must sum
you must sum
he must sum
we must sum
you must sum
they must sum 	I must be summing
you must be summing
he must be summing
we must be summing
you must be summing
they must be summing	I must have summed
you must have summed
he must have summed
we must have summed
you must have summed
they must have summed	I must have been summing
you must have been summing
he must have been summing
we must have been summing
you must have been summing
they must have been summing	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I must not sum
you must not sum
he must not sum
we must not sum
you must not sum
they must not sum 	I must not be summing
you must not be summing
he must not be summing
we must not be summing
you must not be summing
they must not be summing	I must not have summed
you must not have summed
he must not have summed
we must not have summed
you must not have summed
they must not have summed	I must not have been summing
you must not have been summing
he must not have been summing
we must not have been summing
you must not have been summing
they must not have been summing	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I sum?
must you sum?
must he sum?
must we sum?
must you sum?
must they sum? 	must I be summing?
must you be summing?
must he be summing?
must we be summing?
must you be summing?
must they be summing? 	must I have summed?
must you have summed?
must he have summed?
must we have summed?
must you have summed?
must they have summed? 	must I have been summing?
must you have been summing?
must he have been summing?
must we have been summing?
must you have been summing?
must they have been summing? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
must I not sum?
must you not sum?
must he not sum?
must we not sum?
must you not sum?
must they not sum? 	must I not be summing?
must you not be summing?
must he not be summing?
must we not be summing?
must you not be summing?
must they not be summing? 	must I not have summed?
must you not have summed?
must he not have summed?
must we not have summed?
must you not have summed?
must they not have summed? 	must I not have been summing?
must you not have been summing?
must he not have been summing?
must we not have been summing?
must you not have been summing?
must they not have been summing?