I could author you could author she could author we could author you could author they could author
V-ing form
I could be authoring you could be authoring she could be authoring we could be authoring you could be authoring they could be authoring
Perfect
I could have authored you could have authored she could have authored we could have authored you could have authored they could have authored
V-ing perfect
I could have been authoring you could have been authoring she could have been authoring we could have been authoring you could have been authoring they could have been authoring
Negation
Simple form
I couldn't author you couldn't author she couldn't author we couldn't author you couldn't author they couldn't author
V-ing form
I couldn't be authoring you couldn't be authoring she couldn't be authoring we couldn't be authoring you couldn't be authoring they couldn't be authoring
Perfect
I couldn't have authored you couldn't have authored she couldn't have authored we couldn't have authored you couldn't have authored they couldn't have authored
V-ing perfect
I couldn't have been authoring you couldn't have been authoring she couldn't have been authoring we couldn't have been authoring you couldn't have been authoring they couldn't have been authoring
Interrogative form
Simple form
could I author? could you author? could she author? could we author? could you author? could they author?
V-ing form
could I be authoring? could you be authoring? could she be authoring? could we be authoring? could you be authoring? could they be authoring?
Perfect
could I have authored? could you have authored? could she have authored? could we have authored? could you have authored? could they have authored?
V-ing perfect
could I have been authoring? could you have been authoring? could she have been authoring? could we have been authoring? could you have been authoring? could they have been authoring?
Interro-negative form
Simple form
couldn't I author? couldn't you author? couldn't she author? couldn't we author? couldn't you author? couldn't they author?
V-ing form
couldn't I be authoring? couldn't you be authoring? couldn't she be authoring? couldn't we be authoring? couldn't you be authoring? couldn't they be authoring?
Perfect
couldn't I have authored? couldn't you have authored? couldn't she have authored? couldn't we have authored? couldn't you have authored? couldn't they have authored?
V-ing perfect
couldn't I have been authoring? couldn't you have been authoring? couldn't she have been authoring? couldn't we have been authoring? couldn't you have been authoring? couldn't they have been authoring?