English verb conjugation
COULD REFER

Regular verb: refer - referred - referred

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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