# Relationship history for MSHA mine 2501321

Current hierarchy: **Ronald L  Follmer → Mid-Nebraska Aggregate Inc. → Greystone Portable**

- 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

- **controller_controls_mine:** Ronald L  Follmer et al → Greystone Portable; 2000-05-11 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Mid-Nebraska Aggregate Inc. → Greystone Portable; 2023-04-15 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Ronald L  Follmer et al → Mid-Nebraska Aggregate Inc.; 2023-04-15 to current/open; source msha-controller-operator-history