| OI Analytical ( College Station, TX ) | Oil Gas Consultants International, In. ( Tulsa, OK ) | Oil Lift Technology Inc. ( Calgary, CA ) |
| OI Corporation ( College Station, TX ) | Oil & Gas Consultants International Inc. ( Tulsa, OK ) | Oil Lift Technology, Inc. |
| Oi Electric Co., Ltd.( Kanagawa ) | Oil & Gas Consultants International, In. ( Tulsa, OK ) | Oil Lift Technology, Inc.( Calgary ) |
| Oia Intellectuals, Inc. | Oil & Gas Rental Services, Inc. ( Amelia, LA ) | Oil Mallee Company of Australia( Belmont ) |
| OIC Acquisition Corporation ( Redwood Shores, CA ) | Oil & Gas Rental Services, Inc. ( New Orleans, LA ) | Oil Monitoring Systems, Inc. ( Murphy, NC ) |
| OIC Acquisition I Corp ( Redwood Shores, CA ) | Oil and Gas Consultants International, Inc. ( Tulsa, OK ) | Oil Process Systems, Inc ( Allentown, PA ) |
| OIC Acquisition I Corporation ( Redwood Shores, CA ) | OIL AND NATURAL GAS CORPORATION LTD ( Bombay, IN ) | Oil Process Systems, Inc. ( Allentown, PA ) |
| OIC Acquistion I Corporation ( Redwood Shores, CA ) | Oil Caddy, Inc. ( Milwaukee, OR ) | Oil Processing Systems, Inc. ( Allentown, PA ) |
| Oidi Electric Group Co., Ltd. ( Cixi, Zhejiang Province ) | Oil Chem Technologies ( Sugar Land, TX ) | Oil Production Technology Institute ( Dongying, CN ) |
| Oigital Imaging Systems GmbH( Kirchheim/ Teck-Nabern ) | Oil Chem Technologies, Inc. ( Sugar Land, TX ) | Oil Purification Systems, Inc. ( Tampa, FL ) |
| Oigital Imaging Systems GmbH ( Kirchheim/ Teck-Nabern, DE ) | Oil Corporation( Seoul ) | Oil Recovery Systems International ( Irving, TX ) |
| Oikawa Katsunari( Miyagi ) | Oil Country Manufacturing, Inc. | Oil Sands Underground Mining Corp.( Alberta ) |
| Oikawa Katsunari( Shibata-gun ) | Oil Dri Corporation ( Chicago, IL ) | Oil Sands Underground Mining Corporation( Calgary ) |
| Oikawa; Katsunari( Miyagi ) | Oil Dynamics, Inc. ( Tulsa, OK ) | Oil Sands Underground Mining Corporation ( Calgary, CA ) |
| Oikawa; Katsunari ( Miyagi, JP ) | Oil Flow USA, Inc. ( Harrisonburg, VA ) | Oil Sands Underground Mining, Inc. |
| Oikawa; Katsunari( Shibata-gun ) | Oil Industry Engineering, Inc. ( Tomball, TX ) | OIL SANDS UNDERGROUND MINING, INC. ( Calgary, CA ) |
| Oike Industrial Co., Ltd. ( Kyoto, JP ) | OIL LIFT TECHNOLOGY INC. ( Calgary, AB ) | |
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