Simplify the following text for a Grade 14 native English-speaking person.
Original: ( Structural Slumps : The Modern Equilibrium Theory of Employment , Interest and Assets '' ( see Selected PublicationsPhelps also collaborated closely with Luigi Paganetto at the University of Rome Tor Vergata and , between 1988 â `` 98 , as co-organizers of the Villa Mondragone International Seminar .
Simplified: Phelps also worked with Luigi Paganetto at the University of Rome Tor Vergata and , between 1988-98 , they held the Villa Mondragone International Seminar .