Question: Of what nationality are both Dentsply Sirona and Omnicom Group?

Context paragraphs:
Elie Khouri: Elie Khouri (born May 8, 1964) is a Lebanese-French marketing and communications executive in Dubai.  He is the CEO of Omnicom Media Group MENA, the media services division of the Omnicom Group.

Serge Dumont: Serge Dumont (born February 1960), is a French businessman and one of the pioneers in China’s corporate and marketing communications industry.  He currently serves as Omnicom Group Vice Chairman and Chairman, Asia Pacific, and runs Omnicom's Greater China business unit.

TBWA Worldwide: TBWA Worldwide is an international advertising agency whose main headquarters are in Midtown Manhattan, New York City, United States.  The agency is a unit of Omnicom Group, the world's largest advertising agency holding company.  It was founded in 1970 in Paris, France, by William G. Tragos (American, Management), Claude Bonnange (French, Marketing), Uli Wiesendanger (Swiss, Creation), and Paolo Ajroldi (Italian, Client Services).  The first letter of each founder's name provided the initials for the new organization.  They were purchased by the Omnicom Group in 1993.

CEREC: CEREC or Cerec (Chairside Economical Restoration of Esthetic Ceramics, or CEramic REConstruction) is a method of CAD/CAM dentistry developed by W. Mörmann and M. Brandestini at the University of Zurich in 1980 for creating dental restorations. Using CAD/CAM (computer-aided design and computer-aided manufacturing), this process allows dentists to construct, produce, and insert individual ceramic restorations directly at the point of treatment (chairside) in a single appointment, rather than over multiple appointments with lab side working between.  The first applications were successfully carried out on patients in 1985.  The Cerec name is also a brand name of the Sirona companies (as of 2016 Dentsply Sirona) (Sirona Australia, Sirona Germany, Sirona USA, and others), because Sirona grew out of the exclusive licensing of the system by Siemens.

DDB Worldwide: DDB Worldwide Communications Group Inc., known internationally as DDB, is a worldwide marketing communications network.  It is owned by Omnicom Group Inc, one of the world's largest advertising holding companies (revenues US$12.69B according to "Advertising Age" in April 2008).  The international advertising networks Doyle Dane Bernbach and Needham Harper merged their worldwide agency operations to become DDB Needham in 1986.  At that same time the owners of Doyle Dane Bernbach, Needham Harper and BBDO merged their shareholdings to form the worldwide holding company Omnicom.  In 1996, DDB Needham became known as DDB Worldwide.

DDB Mudra: The DDB Mudra Group, a part of the DDB Worldwide Communications Group, is India's first and largest integrated marketing communications and services network.  DDB Worldwide is owned by Omnicom Group Inc, one of the world's largest advertising holding companies.It was earlier known as Mudra Communications Limited and Mudra India.  It also started Mudra Institute of Communications Ahmedabad which is considered India's first academic institution dedicated to communications and advertising studies.  In 2011, Mudra group was acquired by Omnicom Group, subsequently rebranded as DDB Mudra group and merged with DDB Worldwide.  As an advertising agency it is credited with handling successful campaigns of brands and products such as Castrol, Dabur, Future Group, Gulf Oil, and Volkswagen.

Dentsply Sirona: Dentsply Sirona is an American dental equipment maker and dental consumables producer that markets its products in over 120 countries (factories in 21 countries).  It is a leader in consumable dental products.  The present company is largely the result of a merger in 1993 in which Gendex Corporation acquired Dentsply International Inc. for $590 million.

Omnicom Group: Omnicom Group, Inc. is an American global marketing and corporate communications holding company, headquartered in New York City.

Proposed merger of Publicis and Omnicom: The proposed merger of Publicis and Omnicom was a proposed advertising industry merger between Publicis and Omnicom, announced on July 28, 2013.  The resulting company would have been called Publicis Omnicom Group, and would been the world's biggest advertising group with market capitalisation of $35.1 billion, pro-forma revenue of $22.7 billion, and more than 130,000 employees across the world.  After the merger, Publicis Omnicom and WPP would have been the largest advertising groups in the world., followed at a distance by Dentsu and Interpublic Group of Companies.  The Publicis and Omnicom chief executives heralded the proposed operation as a "merger of equals" saying that Publicis and Omnicom shareholders will each hold about 50 percent of the new group's equity.  The group would have had head offices in Paris and New York.

Thomas W. Watson: Thomas Watson is a co-founder and former Vice Chairman of the Omnicom Group, Inc. and consults for Omnicom on management education and leadership development as Dean Emeritus of Omnicom University, Residency and Diversity programs.

Supporting paragraphs: Dentsply Sirona Omnicom Group
Answer: American