<informationTable xmlns="http://www.sec.gov/edgar/document/thirteenf/informationtable">		<infoTable>
			<nameOfIssuer>Aspen Aerogels</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>04523Y105</cusip>
			<value>13144</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>212152</value>
			<shrsOrPrnAmt>
				<sshPrnamt>2710518</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>2710518</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Allergan PLC</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>G0177J108</cusip>
			<value>1285</value>
			<shrsOrPrnAmt>
				<sshPrnamt>5378</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>5378</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Berkshire Hathaway Inc. CL B</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>084670702</cusip>
			<value>2325</value>
			<shrsOrPrnAmt>
				<sshPrnamt>13948</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>13948</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Calpine Corporation</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>131347304</cusip>
			<value>1029</value>
			<shrsOrPrnAmt>
				<sshPrnamt>93118</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>93118</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Cimpress N.V.</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>N20146101</cusip>
			<value>1428</value>
			<shrsOrPrnAmt>
				<sshPrnamt>16573</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>16573</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Commerce Hub Inc.</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>20084V306</cusip>
			<value>546</value>
			<shrsOrPrnAmt>
				<sshPrnamt>35169</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>35169</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>JPMorgan Chase &amp; Co</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>46625H100</cusip>
			<value>3079</value>
			<shrsOrPrnAmt>
				<sshPrnamt>35056</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>35056</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Liberty Broadband Corp</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>530307305</cusip>
			<value>3159</value>
			<shrsOrPrnAmt>
				<sshPrnamt>36557</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>36557</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Liberty Global - Series C</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>G5480U120</cusip>
			<value>1469</value>
			<shrsOrPrnAmt>
				<sshPrnamt>41936</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>41936</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Liberty Global- Lilac Series A</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>G5480U138</cusip>
			<value>531</value>
			<shrsOrPrnAmt>
				<sshPrnamt>23860</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>23860</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Liberty Interactive Corporation QVC Group Ser A</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>53071M104</cusip>
			<value>1249</value>
			<shrsOrPrnAmt>
				<sshPrnamt>62400</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>62400</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Liberty Media Corp Series C Sirius XM Group</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>531229607</cusip>
			<value>1204</value>
			<shrsOrPrnAmt>
				<sshPrnamt>31038</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>31038</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Moodys Corp</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>615369105</cusip>
			<value>1029</value>
			<shrsOrPrnAmt>
				<sshPrnamt>9181</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>9181</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>Microsoft Corp</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>594918104</cusip>
			<value>1810</value>
			<shrsOrPrnAmt>
				<sshPrnamt>27481</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>27481</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>S&amp;P Global Inc.</nameOfIssuer>
			<titleOfClass>Common</titleOfClass>
			<cusip>78409V104</cusip>
			<value>1330</value>
			<shrsOrPrnAmt>
				<sshPrnamt>10170</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>OTR</investmentDiscretion>
			<otherManager>n/a</otherManager>
			<votingAuthority>
				<Sole>0</Sole>
				<Shared>0</Shared>
				<None>10170</None>
			</votingAuthority>
		</infoTable>
</informationTable>
