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          }
        ],
        "assumptions": []
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        "key": "center",
        "label": "Center",
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        "assumptions": []
      },
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        "key": "pi1",
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            "source": "conrad",
            "locator": "Lecture 16, including (16.6), and Appendix P: Spin(n) as the simply connected double cover for n ≥ 3"
          }
        ],
        "assumptions": []
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        "key": "connected",
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        "assumptions": []
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            "text": "SU(2) is diffeomorphic to S³. The central quotient by {±I} is SO(3).",
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            "text": "Angular momentum, spin, weak isospin, and the basic example of a spin cover.",
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        "Pavel Etingof"
      ],
      "url": "https://ocw.mit.edu/courses/18-755-lie-groups-and-lie-algebras-ii-spring-2024/mit18_755_s24_lec15.pdf",
      "kind": "lecture-notes",
      "locatorHint": "Section 41, printed pages 218–225.",
      "licenseNote": "Linked MIT OpenCourseWare notes; definitions and classification facts are summarized in original prose."
    },
    {
      "id": "garrett-isogenies",
      "title": "Sporadic isogenies to orthogonal groups",
      "authors": [
        "Paul Garrett"
      ],
      "url": "https://ncatlab.org/nlab/files/Garrett-SporadicIsogenies.pdf",
      "kind": "lecture-notes",
      "locatorHint": "May 7, 2015 notes, Sections 2.1–2.11. The linked file is an accessible mirror of the author’s notes.",
      "licenseNote": "Author’s lecture notes linked at an accessible mirror. No redistribution license is inferred; matrix constructions are explained independently."
    }
  ],
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