CSIO may refer to:
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Central Scientific Instruments Organisation
Central Scientific Instruments Organisation is a Chandigarh, India-based national laboratory dedicated to research, design and development of scientific, and industrial instruments. It is one of the constituent laboratories of the Council of Sci ...
, an Indian national laboratory dedicated to research, design and development of scientific and industrial instruments
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Centre for Study of Insurance Operations, the Canadian property and casualty insurance industry's nonprofit association of insurers, brokers and software providers
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City State of the Invincible Overlord
''City State of the Invincible Overlord'' is a fantasy role-playing game supplement originally published by Judges Guild in 1976. It was the first published fantasy role-playing game city setting, designed for use with '' Dungeons & Dragons'' (''D ...
, a 1976
Judges Guild product that was the first published fantasy role-playing game city setting
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Concours de Saut International Officiel, a ranking system for the equestrian competition show jumping
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