# Relationship history for MSHA mine 0405302

Current hierarchy: **MDU Resources Group Inc → KRC Aggregate Inc → MARTIN SAND AND GRAVEL**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-18T09:31:49.615908+00:00

## Valid-time edges

- **controller_controls_mine:** MDU Resources Group Inc → MARTIN SAND AND GRAVEL; 1992-05-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Martin Sand & Gravel → MARTIN SAND AND GRAVEL; 1997-02-01 to 2000-03-28; source msha-controller-operator-history
- **controller_controls_mine:** Dennis  Glassburn → MARTIN SAND AND GRAVEL; 1997-02-01 to 2000-03-28; source msha-controller-operator-history
- **controller_controls_operator:** Dennis  Glassburn → Martin Sand & Gravel; 1997-02-01 to 2000-03-28; source msha-controller-operator-history
- **operator_operates_mine:** KRC Aggregate Inc → MARTIN SAND AND GRAVEL; 2000-03-29 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** MDU Resources Group Inc → KRC Aggregate Inc; 2000-03-29 to current/open; source msha-controller-operator-history