Documents released yesterday by the University of the District of Columbia show that Cassandra A. Simmons, a longtime associate of President Robert L. Green, received nearly $3,000 more in travel expenses from university funds than previously disclosed and that she accompanied him twice on trips to Boston.

On one of those trips, documents show, Simmons flew from Detroit to Washington and stayed at the Madison Hotel before she and Green traveled first-class the next day to Boston. There they spent a three-day weekend working on a book Green was writing about school desegregation, according to a university spokesman.

A hand-written notation on the records of the trip indicates that $407 charged to Green's American Express card was for a "reception." However, other documents obtained by The Post show that the $407 bill covered two hotel rooms and 10 room-service charges.

On a second trip to Boston, available documents show that Simmons spent $664 of UDC funds for airfare and hotel bills to attend "a higher education conference." During that three-day trip, a car was rented in Green's name in Boston and driven 299 miles, also at UDC expense, according to UDC records.

The documents obtained by The Post under the D.C. Freedom of Information Act include vouchers, receipts and summations of expenditures from the university's representation fund, which comprises a mixture of public funds and fees collected by the university to cover expenses the president incurs while on official business. Gilbert Maddox, a UDC spokesman, said yesterday that university officials would have to study the records before they could provide explanations of the newly disclosed expenditures.

Earlier this week, Maddox said Simmons and Green traveled to Boston in May to put the finishing touches on Green's book about school desegregation, which was published last week.

"She was a major force in the final publishing of his book," Maddox said.

Since early June, Green has repeatedly declined to be interviewed by The Post about the controversy over his expenditures.

The documents also show that since taking office in September 1983 Green has taken 10 trips totaling $3,371 that were not included in a travel log that the university issued to The Post in June.

Also, vouchers from the president's representation fund showed that Green's wife Lettie, was reimbursed $858 for a four-day trip to San Francisco to attend a funeral in December 1983.

The new documents also provide additional details of Green's expenditures of UDC funds for personal items, including flowers that he and his three sons sent to his wife on Mother's Day in 1984.

The FBI last week began an investigation of alleged financial improprieties at the publicly financed university.

In a report issued last week, D.C. Auditor Otis H. Troupe concluded that Green owed UDC $13,000 in funds Troupe said he had misspent.

Meanwhile, UDC trustee N. Joyce Payne yesterday became the fourth board member to call on Green to step aside until the controversy about his finances is resolved.

"I think the president should step aside and I think there needs to be a perceptible change in the fiscal management practices at the university," she said. "Given the magnitude of media exposure and public concern we cannot continue to tolerate the kind of disruption that has taken place at the institution over the last three months."

The documents released yesterday are from Green's representation fund. These records, for fiscal 1984, were the subject of Troupe's final audit report issued last week. The fund was also reviewed by a national accounting firm hired by the 15-member board of trustees.

Neither Troupe's report nor the accounting firm, Coopers & Lybrand, mentioned the bulk of $2,972 of expenditures from the representation fund incurred by Simmons, an assistant professor at Michigan State University, where Green was a dean before coming to UDC.

Simmons, a former student of Green's, received $37,200 from UDC and $10,000 from the D.C. government for consulting services since Green was named UDC president, according to documents previously released by the university and the D.C. government.

Simmons' expenses for five trips she took to Washington to advise Green as a consultant were paid for by UDC, the representation records show. She stayed in hotels where basic room charges ranged from $119 to $155 per night.

On one of those trips, in October 1983, Green personally paid the $138 for Simmons' hotel and meal expenses at the Shoreham and then was reimbursed by the university, according to receipts and vouchers.

The $138 hotel bill included a $23 tab for room service breakfast for two persons charged to Simmons' room and signed with Green's name, according to university records.

Among the trips by Green and his wife not previously reported by the university were 12 trips to Michigan, consisting of nine by Green and three by his wife. Lettie Green accompanied her husband on one of the Michigan trips.

Green's contract states that UDC will cover his wife's travel expenses when she is traveling with him on official business.

Records of the representation fund show a variety of charges for flowers, including $42.50 for a dozen salmon roses sent by Green's son, Kurt, to Michelle Grundy, a UDC staffer; $22.50 for flowers to Mayor Marion Barry on his birthday last year, and $27.50 for flowers to former deputy mayor Ivanhoe Donaldson, a former Michigan State student, on his birthday in October 1983.