He asserts that she stole money from him.
Our department have already consulted [the] local Marketing Training Centre, which asserted that these employees are eligible to take the course. (Certificate in Advanced English; C1; Russian)
She has to learn to assert herself.
Such an attitude may also be the result of little pangs of homesickness or of our need to assert ourselves, to feel superior in a foreign country. (Certificate of Proficiency in English; C2; French)
She soon asserted her authority as leader.
He can assert his authority over all the boys who are there. (Certificate of Proficiency in English; C2; Italian)