2024 30 USC 4c – Investigation of sub-bituminous and lignite coal

2023 30 USC 4c – Investigation of sub-bituminous and lignite coal

2022 30 USC 4c – Investigation of sub-bituminous and lignite coal

2021 30 USC 4c – Investigation of sub-bituminous and lignite coal

2020 30 USC 4c – Investigation of sub-bituminous and lignite coal

2018 30 USC 4c – Investigation of sub-bituminous and lignite coal

2017 30 USC 4c – Investigation of sub-bituminous and lignite coal

2015 30 USC 4c – Investigation of sub-bituminous and lignite coal

2014 30 USC 4c – Investigation of sub-bituminous and lignite coal

2013 30 USC 4c – Investigation of sub-bituminous and lignite coal

2012 30 USC 4c – Investigation of sub-bituminous and lignite coal

2010 30 USC 4c – Investigation of sub-bituminous and lignite coal