English verb conjugation
CAN REF

Regular verb: ref - refed - refed

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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