In limited instances, it is to the benefit of Stanford faculty to permit persons who have not yet obtained a Ph.D. (or its foreign equivalent), or who are not recognized experts in their fields, to engage in research on the Stanford campus using Stanford research facilities. Such instances might include students at other universities who are engaged in graduate-level research in a field of interest to the faculty member, or a person doing a laboratory rotation as part of a larger research study or grant. Invitations are valid for one calendar year. The status may be extended once for an additional calendar year. Extensions beyond the initial approval date require submission of an updated letter of invitation with new dates to Graduate Admissions, Office of the University Registrar and to the visiting student researcher.