• 1 · Religion and Magic
• 2 · Nature
• 3 · Human Being, Man in General
• 4 · Society, Civilization, Culture
• 5 · Abstract Ideas and Concepts
• 6 · History
• 7 · Bible
• 8 · Literature
• 9 · Classical Mythology and Ancient History

• Top
• 4 · Society, Civilization, Culture
• 49 · education, science and learning
• 49D · mathematics
• 49D3 · planimetry, geometry
• 49D32 · line (~ planimetry, geometry)
• 49D321 · straight line

49D3213 · parallel lines