บทคัดย่อ, ทางเรขาคณิต, แสงอาทิตย์, มีศูนย์กลางร่วมกัน, ศูนย์, ฉากหลัง, ภูมิหลัง, ภาพประกอบ, แบบแผน, เวกเตอร์, ออกแบบ
Public Domain
ภาพถ่ายปลอดค่าลิขสิทธิ์ที่เกี่ยวข้อง
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