Complex sentence: Since 2011, a number of commercial companies have received exploration contracts these include subsidiaries of larger companies like Lockheed Martin, DEME, Keppel Corporation and China Minmetals and smaller companies like Nauru Ocean Resources Inc and Tonga Offshore Mining Limited.
Split into simpler sentences: Since 2011, a number of commercial companies have received exploration contracts. These include subsidiaries of larger companies like Lockheed Martin, DEME, Keppel Corporation and China Minmetals and smaller companies like Nauru Ocean Resources Inc and Tonga Offshore Mining Limited.