English verb conjugation
CAN REFER

Regular verb: refer - referred - referred

Affirmation

Simple form	V-ing form
I can refer you can refer she can refer we can refer you can refer they can refer	I can be referring you can be referring she can be referring we can be referring you can be referring they can be referring
Perfect	V-ing perfect
I can have referred you can have referred she can have referred we can have referred you can have referred they can have referred	I can have been referring you can have been referring she can have been referring we can have been referring you can have been referring they can have been referring

Negation

Simple form	V-ing form
I can't refer you can't refer she can't refer we can't refer you can't refer they can't refer	I can't be referring you can't be referring she can't be referring we can't be referring you can't be referring they can't be referring
Perfect	V-ing perfect
I can't have referred you can't have referred she can't have referred we can't have referred you can't have referred they can't have referred	I can't have been referring you can't have been referring she can't have been referring we can't have been referring you can't have been referring they can't have been referring

Interrogative form

Simple form	V-ing form
can I refer? can you refer? can she refer? can we refer? can you refer? can they refer?	can I be referring? can you be referring? can she be referring? can we be referring? can you be referring? can they be referring?
Perfect	V-ing perfect
can I have referred? can you have referred? can she have referred? can we have referred? can you have referred? can they have referred?	can I have been referring? can you have been referring? can she have been referring? can we have been referring? can you have been referring? can they have been referring?

Interro-negative form

Simple form	V-ing form
can't I refer? can't you refer? can't she refer? can't we refer? can't you refer? can't they refer?	can't I be referring? can't you be referring? can't she be referring? can't we be referring? can't you be referring? can't they be referring?
Perfect	V-ing perfect
can't I have referred? can't you have referred? can't she have referred? can't we have referred? can't you have referred? can't they have referred?	can't I have been referring? can't you have been referring? can't she have been referring? can't we have been referring? can't you have been referring? can't they have been referring?