could refer
Verbo regular: refer - referred- referred

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could refer
you could refer
she could refer
we could refer
you could refer
they could refer 	I could be referring
you could be referring
she could be referring
we could be referring
you could be referring
they could be referring	I could have referred
you could have referred
she 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
she could have been referring
we could have been referring
you could have been referring
they could have been referring	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could not refer
you could not refer
she could not refer
we could not refer
you could not refer
they could not refer 	I could not be referring
you could not be referring
she could not be referring
we could not be referring
you could not be referring
they could not be referring	I could not have referred
you could not have referred
she could not have referred
we could not have referred
you could not have referred
they could not have referred	I could not have been referring
you could not have been referring
she could not have been referring
we could not have been referring
you could not have been referring
they could not have been referring	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I refer?
could you refer?
could she refer?
could we refer?
could you refer?
could they refer? 	could I be referring?
could you be referring?
could she be referring?
could we be referring?
could you be referring?
could they be referring? 	could I have referred?
could you have referred?
could she 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 she have been referring?
could we have been referring?
could you have been referring?
could they have been referring? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I not refer?
could you not refer?
could she not refer?
could we not refer?
could you not refer?
could they not refer? 	could I not be referring?
could you not be referring?
could she not be referring?
could we not be referring?
could you not be referring?
could they not be referring? 	could I not have referred?
could you not have referred?
could she not have referred?
could we not have referred?
could you not have referred?
could they not have referred? 	could I not have been referring?
could you not have been referring?
could she not have been referring?
could we not have been referring?
could you not have been referring?
could they not have been referring?