English verb conjugation
MUST REF

Regular verb: ref - refed - refed

Affirmation

Simple form	V-ing form
I must ref you must ref he must ref we must ref you must ref they must ref	I must be refing you must be refing he must be refing we must be refing you must be refing they must be refing
Perfect	V-ing perfect
I must have refed you must have refed he must have refed we must have refed you must have refed they must have refed	I must have been refing you must have been refing he must have been refing we must have been refing you must have been refing they must have been refing

Negation

Simple form	V-ing form
I mustn't ref you mustn't ref he mustn't ref we mustn't ref you mustn't ref they mustn't ref	I mustn't be refing you mustn't be refing he mustn't be refing we mustn't be refing you mustn't be refing they mustn't be refing
Perfect	V-ing perfect
I mustn't have refed you mustn't have refed he mustn't have refed we mustn't have refed you mustn't have refed they mustn't have refed	I mustn't have been refing you mustn't have been refing he mustn't have been refing we mustn't have been refing you mustn't have been refing they mustn't have been refing

Interrogative form

Simple form	V-ing form
must I ref? must you ref? must he ref? must we ref? must you ref? must they ref?	must I be refing? must you be refing? must he be refing? must we be refing? must you be refing? must they be refing?
Perfect	V-ing perfect
must I have refed? must you have refed? must he have refed? must we have refed? must you have refed? must they have refed?	must I have been refing? must you have been refing? must he have been refing? must we have been refing? must you have been refing? must they have been refing?

Interro-negative form

Simple form	V-ing form
mustn't I ref? mustn't you ref? mustn't he ref? mustn't we ref? mustn't you ref? mustn't they ref?	mustn't I be refing? mustn't you be refing? mustn't he be refing? mustn't we be refing? mustn't you be refing? mustn't they be refing?
Perfect	V-ing perfect
mustn't I have refed? mustn't you have refed? mustn't he have refed? mustn't we have refed? mustn't you have refed? mustn't they have refed?	mustn't I have been refing? mustn't you have been refing? mustn't he have been refing? mustn't we have been refing? mustn't you have been refing? mustn't they have been refing?