Reference - Person other than the subject of a background investigation, identified as having knowledge of the subject. References are characterized by source and type. There are two sources: listed (meaning the subject of the investigation identified the reference on the Personnel Security Questionnaire) and developed (meaning an investigator, in the course of pursuing leads, identified the reference as someone knowledgeable of the subject). There are six types: education (a faculty member or school administrator at a school attended by the subject who had knowledge of the subject when a student), employment/supervisor (a person with management responsibilities for the subject), co-worker (a colleague with knowledge of the subject's on-the-job behavior), neighborhood (a person living in the subject's neighborhood who has knowledge of the subject), friend/associate (a person knowing the subject socially, preferably away from both work and home), knowledgeable person (a person who knows the subject in some other context; for example, a banker or attorney or real estate agent who conducts business on behalf of the subject; or a clerk in a store where the subject shops frequently). A specific reference can be categorized as more than one type: for example, someone who is both an office mate and fellow member of a softball team may be both be a co-worker reference and a friend/associate reference.