List of metro systems - Wikipedia
File:Sofia metro at Musagenitsa.jpg - Wikimedia Commons
File:Sofia-metro-schema-01.svg - Wikimedia Commons
File:Sofia Metro Logo.svg - Wikimedia Commons
Serdika Metro Station - Wikipedia
List of Thessaloniki Metro stations - Wikipedia
File:Sofia Metro-Map-en.png - Wikimedia Commons
Sofia Metro - Wikipedia
File:Sofia Metro Station Serdica II October 2012 PD 5.jpg - Wikimedia Commons
Sofia Metro - Wikipedia
Siemens Inspiro - Wikipedia
File:Sofia-metro-schema-01.svg - Wikimedia Commons
File:Metro Station, Sofia, Bulgaria.jpg - Wikipedia
Sofia Metro - Wikipedia
Vitosha Metro Station - Wikipedia
File:Metro serdika.jpg - Wikipedia
Sofia Metro - Transport Wiki
Medium-capacity rail system - Wikipedia
Sofia Metro - Transport Wiki
File:Central railway station (Sofia Metro) 2012 PD 3.jpg - Wikimedia Commons
Moesia Metro Station - Wikipedia
Sofia Metro Map | Metro Line Map
File:Metro Map Sofia (German).svg - Wikimedia Commons
File:Sofia-metro-schema-01.svg - Wikimedia Commons
Metro de Sofía - Wikipedia, la enciclopedia libre
Obelya Metro Station - Wikipedia
