<informationTable xmlns="http://www.sec.gov/edgar/document/thirteenf/informationtable">		<infoTable>
			<nameOfIssuer>Anadarko Petroleum</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>032511107</cusip>
			<value>142200</value>
			<shrsOrPrnAmt>
				<sshPrnamt>1401814</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>1401814</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Aspen Aerogels</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>04523Y105</cusip>
			<value>31927</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>317478</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>31204</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>44812</value>
			<shrsOrPrnAmt>
				<sshPrnamt>764052</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>764052</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Direct TV</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>25490A309</cusip>
			<value>970</value>
			<shrsOrPrnAmt>
				<sshPrnamt>11212</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>11212</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Express Scripts</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>30219G108</cusip>
			<value>1705</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>1237</value>
			<shrsOrPrnAmt>
				<sshPrnamt>40025</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>40025</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>JPMorgan Chase &amp; Co</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>466625H10</cusip>
			<value>2016</value>
			<shrsOrPrnAmt>
				<sshPrnamt>33461</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>33461</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Liberty Global - Series C</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>G5480U120</cusip>
			<value>1044</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>1146</value>
			<shrsOrPrnAmt>
				<sshPrnamt>19122</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>19122</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Mastercard CL A</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>57636Q104</cusip>
			<value>659</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>2232</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>498</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>1240</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>986</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>872</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>2319</value>
			<shrsOrPrnAmt>
				<sshPrnamt>17678</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>17678</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Viacom</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>92553P201</cusip>
			<value>1398</value>
			<shrsOrPrnAmt>
				<sshPrnamt>18169</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>18169</None>
			</votingAuthority>
		</infoTable>
</informationTable>
