{"type": {"key": "/type/work"}, "title": "Letters sent by the Topographical Bureau of the War Department and by successor divisions in the Office of the Chief of Engineers, 1829-1870", "subjects": ["Sources", "History", "Topographical surveying", "Military engineering", "United States. Topographical Bureau", "United States", "United States. Army. Corps of Engineers"], "subject_places": ["United States"], "authors": [{"type": {"key": "/type/author_role"}, "author": {"key": "/authors/OL18558A"}}], "key": "/works/OL35562248W", "latest_revision": 2, "revision": 2, "created": {"type": "/type/datetime", "value": "2023-05-27T18:37:44.497759"}, "last_modified": {"type": "/type/datetime", "value": "2025-07-16T20:37:49.714455"}}