A rumor or rumour (see spelling differences) is often viewed as "an unverified account or explanation of events circulating from person to person and pertaining to an object, event, or issue in public concern" (33) However, a review of the research on rumor conducted by Pendleton in 1998 found that research across sociology, psychology, and communication studies had widely varying definitions of rumor. Thus, rumor is a concept that lacks a particular definition in the social sciences. But most theories agree that rumor involves some kind of a statement whose veracity is not quickly or ever confirmed. In addition, some scholars have identified rumor as a subset of propaganda, the latter another notoriously difficult concept to define. A pioneer of propaganda studies, Harold Lasswell defined propaganda in 1927 as referring "solely to the control of opinion by significant symbols, or, to speak more concretely and less accurately, by stories, rumors, reports, pictures, and other forms of social communication" (1927:9). Rumors are also often discussed with regard to "misinformation" and "disinformation" (the former often seen as simply false and the latter seen as deliberately false, though usually from a government source given to the media or a foreign government). Rumors thus have often been viewed as particular forms of other communication concepts.