# Relationship history for MSHA mine 3603336

Current hierarchy: **AOI Coal Company → Willowbrook Mining Company → Willowbrook Strips**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **operator_operates_mine:** Willowbrook Mining Company → Willowbrook Strips; 1950-01-01 to 1978-01-11; source msha-controller-operator-history
- **controller_controls_mine:** Sartori James → Willowbrook Strips; 1950-01-01 to 1978-01-11; source msha-controller-operator-history
- **controller_controls_operator:** Sartori James → Willowbrook Mining Company; 1950-01-01 to 1978-01-11; source msha-controller-operator-history
- **operator_operates_mine:** Willowbrook Mining Company → Willowbrook Strips; 1978-01-12 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** AOI Coal Company → Willowbrook Strips; 1978-01-12 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** AOI Coal Company → Willowbrook Mining Company; 1978-01-12 to current/open; source msha-controller-operator-history