The provided content discusses the causes of variation orders in the construction industry, with a focus on Nigeria. The articles explore various aspects of project management, including project variation management, evaluation of construction projects under engineering variation, and the impact of internal vs. external customers on variation. Other topics include spatio-temporal variation of stream-aquifer interaction, understanding the effect of variation in production systems, and severity of variation order factors affecting construction project performance. The content aims to provide insights into the causes and effects of variation orders in the Nigerian construction industry.