<informationTable xmlns="http://www.sec.gov/edgar/document/thirteenf/informationtable">		<infoTable>
			<nameOfIssuer>Anadarko Petroleum</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>032511107</cusip>
			<value>153457</value>
			<shrsOrPrnAmt>
				<sshPrnamt>1401814</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>1451814</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Aspen Aerogels</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>04523Y105</cusip>
			<value>34999</value>
			<shrsOrPrnAmt>
				<sshPrnamt>3167322</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>3167322</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>BOK Financial</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>05561Q201</cusip>
			<value>318051</value>
			<shrsOrPrnAmt>
				<sshPrnamt>4775536</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>4775536</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Petroleo Brasileiros</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>71654V408</cusip>
			<value>32171</value>
			<shrsOrPrnAmt>
				<sshPrnamt>2199000</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>2199000</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Unit Corporation</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>909218109</cusip>
			<value>60896</value>
			<shrsOrPrnAmt>
				<sshPrnamt>884730</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>1339515</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Direct TV</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>25490A309</cusip>
			<value>1803</value>
			<shrsOrPrnAmt>
				<sshPrnamt>21211</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>21211</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Express Scripts</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>30219G108</cusip>
			<value>1673</value>
			<shrsOrPrnAmt>
				<sshPrnamt>24137</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>24137</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Gaming &amp; Leisure Properties</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>36467J108</cusip>
			<value>1130</value>
			<shrsOrPrnAmt>
				<sshPrnamt>33271</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>33271</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>JPMorgan Chase &amp; Co</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>466625H10</cusip>
			<value>1786</value>
			<shrsOrPrnAmt>
				<sshPrnamt>31004</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>31004</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Liberty Global - Series C</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>G5480U120</cusip>
			<value>1077</value>
			<shrsOrPrnAmt>
				<sshPrnamt>25453</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>25453</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Lorillard Inc</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>544147101</cusip>
			<value>759</value>
			<shrsOrPrnAmt>
				<sshPrnamt>12451</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>17074</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Mastercard CL A</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>57636Q104</cusip>
			<value>655</value>
			<shrsOrPrnAmt>
				<sshPrnamt>8921</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>8921</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Microsoft Cors</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>594918104</cusip>
			<value>2008</value>
			<shrsOrPrnAmt>
				<sshPrnamt>48155</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>48155</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Penn National Gaming</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>707569109</cusip>
			<value>539</value>
			<shrsOrPrnAmt>
				<sshPrnamt>44381</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>44381</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Philip Morris</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>718172109</cusip>
			<value>1253</value>
			<shrsOrPrnAmt>
				<sshPrnamt>14863</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>14863</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Starz Liberty</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>85571Q102</cusip>
			<value>888</value>
			<shrsOrPrnAmt>
				<sshPrnamt>29808</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>29808</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Taminco</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>87509U106</cusip>
			<value>777</value>
			<shrsOrPrnAmt>
				<sshPrnamt>33403</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>33403</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Valeant Pharmaceuticals</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>91911K102</cusip>
			<value>1683</value>
			<shrsOrPrnAmt>
				<sshPrnamt>13343</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>11418</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Viacom</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>92553P201</cusip>
			<value>988</value>
			<shrsOrPrnAmt>
				<sshPrnamt>11395</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>11395</None>
			</votingAuthority>
		</infoTable>
</informationTable>
