I must found you must found she must found we must found you must found they must found
V-ing form
I must be founding you must be founding she must be founding we must be founding you must be founding they must be founding
Perfect
I must have founded you must have founded she must have founded we must have founded you must have founded they must have founded
V-ing perfect
I must have been founding you must have been founding she must have been founding we must have been founding you must have been founding they must have been founding
Negation
Simple form
I must not found you must not found she must not found we must not found you must not found they must not found
V-ing form
I must not be founding you must not be founding she must not be founding we must not be founding you must not be founding they must not be founding
Perfect
I must not have founded you must not have founded she must not have founded we must not have founded you must not have founded they must not have founded
V-ing perfect
I must not have been founding you must not have been founding she must not have been founding we must not have been founding you must not have been founding they must not have been founding
Interrogative form
Simple form
must I found? must you found? must she found? must we found? must you found? must they found?
V-ing form
must I be founding? must you be founding? must she be founding? must we be founding? must you be founding? must they be founding?
Perfect
must I have founded? must you have founded? must she have founded? must we have founded? must you have founded? must they have founded?
V-ing perfect
must I have been founding? must you have been founding? must she have been founding? must we have been founding? must you have been founding? must they have been founding?
Interro-negative form
Simple form
must I not found? must you not found? must she not found? must we not found? must you not found? must they not found?
V-ing form
must I not be founding? must you not be founding? must she not be founding? must we not be founding? must you not be founding? must they not be founding?
Perfect
must I not have founded? must you not have founded? must she not have founded? must we not have founded? must you not have founded? must they not have founded?
V-ing perfect
must I not have been founding? must you not have been founding? must she not have been founding? must we not have been founding? must you not have been founding? must they not have been founding?