an Entity references as follows:
The 2017–18 Tour de Ski was the 12th edition of the Tour de Ski, part of the 2017–18 FIS Cross-Country World Cup. The World Cup stage event began in Lenzerheide, Switzerland, on December 30, 2017, and ended in Val di Fiemme, Italy, on January 7, 2018. The cups were defended by Heidi Weng (Norway) and Sergey Ustiugov (Russia).