# Relationship history for MSHA mine 0101906

Current hierarchy: **Johnson Richard → Hy-Grade Coal Company Inc → Rocky Hollow Strip**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Johnson Richard → Rocky Hollow Strip; 1976-12-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Hy-Grade Coal Company Inc → Rocky Hollow Strip; 1978-08-01 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Johnson Richard → Hy-Grade Coal Company Inc; 1978-08-01 to current/open; source msha-controller-operator-history