English verb conjugation
CAN REFEREE

Regular verb: referee - refereed - refereed

Affirmation

Simple form	V-ing form
I can referee you can referee she can referee we can referee you can referee they can referee	I can be refereeing you can be refereeing she can be refereeing we can be refereeing you can be refereeing they can be refereeing
Perfect	V-ing perfect
I can have refereed you can have refereed she can have refereed we can have refereed you can have refereed they can have refereed	I can have been refereeing you can have been refereeing she can have been refereeing we can have been refereeing you can have been refereeing they can have been refereeing

Negation

Simple form	V-ing form
I can't referee you can't referee she can't referee we can't referee you can't referee they can't referee	I can't be refereeing you can't be refereeing she can't be refereeing we can't be refereeing you can't be refereeing they can't be refereeing
Perfect	V-ing perfect
I can't have refereed you can't have refereed she can't have refereed we can't have refereed you can't have refereed they can't have refereed	I can't have been refereeing you can't have been refereeing she can't have been refereeing we can't have been refereeing you can't have been refereeing they can't have been refereeing

Interrogative form

Simple form	V-ing form
can I referee? can you referee? can she referee? can we referee? can you referee? can they referee?	can I be refereeing? can you be refereeing? can she be refereeing? can we be refereeing? can you be refereeing? can they be refereeing?
Perfect	V-ing perfect
can I have refereed? can you have refereed? can she have refereed? can we have refereed? can you have refereed? can they have refereed?	can I have been refereeing? can you have been refereeing? can she have been refereeing? can we have been refereeing? can you have been refereeing? can they have been refereeing?

Interro-negative form

Simple form	V-ing form
can't I referee? can't you referee? can't she referee? can't we referee? can't you referee? can't they referee?	can't I be refereeing? can't you be refereeing? can't she be refereeing? can't we be refereeing? can't you be refereeing? can't they be refereeing?
Perfect	V-ing perfect
can't I have refereed? can't you have refereed? can't she have refereed? can't we have refereed? can't you have refereed? can't they have refereed?	can't I have been refereeing? can't you have been refereeing? can't she have been refereeing? can't we have been refereeing? can't you have been refereeing? can't they have been refereeing?