Modifiers matching observer:

• trained,
• careful,
• objective,
• key,
• inexperienced,
• concerned,
• professional,
• influential,
• experienced,
• everyday,
• naive,
• external,
• special,
• outside,
• casual,
• dedicated,
• social,
• responsible,
• skilled,
• independent,
• impartial,
• interested,
• knowledgeable,
• primary,
• familiar,
• unofficial,
• foreign,
• contemporary,
• lay,

Simple categories matching unofficial:

• information,
• observer,
• traveler,
• record,
• document,
• material,
• writing,
• account,
• writer,
• history,