Simple categories matching grey:

• material,
• action,
• literature,
• structure,
• fabric,
• squirrel,
• source,
• color,

Members with property grey:

• report,
• doctoral_thesis,
• denim_fabric,
• statement,
• dissertation,
• pons,
• thesis,
• claustrum,
• conference_report,
• pile,
• conference_papers,
• working_document,
• technical_report,
• occasional_papers,
• meeting_papers,
• institutional_report,
• annual_report,
• internal_report,
• policy_document,
• literature_review,
• government_report,
• government_study,
• pamphlet,
• journal,
• fda_submission,
• government_document,
• discussion_papers,
• article,
• draft,
• working_papers,
• patent,
• water,
• web_papers,
• basal_ganglion,
• research_report,
• internal_papers,
• terry,
• unpublished_document,
• published_study,
• consultant_report,
• book_chapter,
• unpublished_thesis,
• thalamus,
• white_papers,
• unpublished_report,
• chapter,
• policy_papers,
• diary,
• organizational_report,
• dissertation_thesis,
• unpublished_papers,
• caudate,
• policy,
• waste_minimisation,
• semester_assignment,
• current_literature,
• web_journal,
• unpublished_manuscript,
• energy_efficiency,
• terry_towelling,
• chenille,
• grey_squirrel,
• grey,
• strategy_papers,
• lecture_note,
• speech,
• state-government_document,
• roads,
• research_papers,