These are organizations from which funds are available to support causes, including medical and scientific research. Some derive funds wholly or partly from government sources, others from gifts and/or bequests, and a few encourage additional support in the form of charitable donations from members of the general public. Several foundations have long played a prominent role in the advance of medical science and experimental or demonstration projects, such as community clinics. These include the Rockefeller Foundation, the Ford Foundation, the Milbank Memorial Fund, the Nuffield Trust, the Commonwealth Fund, the Bill & Melinda Gates Foundation, the Wolfson Foundation, and many others. Many activities of foundations in low- and middle-income nations, such as provision and evaluation of family planning services, often resemble the activities of nongovernmental organizations.