sentences:  However, after 9/11 it became increasingly difficult for many overseas students to get permission to study in the United States, and that situation had a highly adverse impact on Thunderbird's enrollment.The global financial crisis of 2008 had a similarly harmful effect on Thunderbird's enrollment as students from overseas found it more difficult to afford studying abroad.In 2001, the school began to offer a Master of Business Administration (MBA) in International Management, replacing the previously offered Master of International Management.