<informationTable xmlns="http://www.sec.gov/edgar/document/thirteenf/informationtable">		<infoTable>
			<nameOfIssuer>Hallador Energy Company</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>40609P105</cusip>
			<value>1307</value>
			<shrsOrPrnAmt>
				<sshPrnamt>361094</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<otherManager>1, 2</otherManager>
			<votingAuthority>
				<Sole>361094</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Antero Midstream Corp</nameOfIssuer>
			<titleOfClass>COM SHS REPSTG</titleOfClass>
			<cusip>03675Y103</cusip>
			<value>25252</value>
			<shrsOrPrnAmt>
				<sshPrnamt>3412464</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<otherManager>1, 2</otherManager>
			<votingAuthority>
				<Sole>3412464</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Mid Con Energy Partners</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>59560V109</cusip>
			<value>15</value>
			<shrsOrPrnAmt>
				<sshPrnamt>37207</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<otherManager>1, 2</otherManager>
			<votingAuthority>
				<Sole>37207</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Antero Res Corp</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>03674X106</cusip>
			<value>1966</value>
			<shrsOrPrnAmt>
				<sshPrnamt>651033</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<otherManager>1, 2</otherManager>
			<votingAuthority>
				<Sole>651033</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
</informationTable>
