Simplify the following text for a Grade 8 native English-speaking person.
Original: Since its inception , TWAS 's operational expenses have largely been covered by generous contributions of the Italian government ; since 1991 UNESCO has been responsible for the administration of TWAS finance and staff on the basis of an agreement signed by the director general of UNESCO and the president of TWAS .
Simplified: The director general of UNESCO and the president of TWAS signed an agreement . UNESCO has managed TWAS finance and staff since 1991 .