Znamky vsech 4 zemi v prodeji i v ČR:
http://philatelynews.com/2011/czech-republic/20-years-of-the-visegrad-group-czech-republic/
http://philatelynews.com/2011/slovakia/20th-anniversary-of-the-foundation-of-the-visegrad-group-slovakia/
http://philatelynews.com/2011/poland/20th-anniversary-of-the-foundation-of-the-visegrad-group-poland/
http://philatelynews.com/2011/hungary/20th-anniversary-of-the-visegrad-group-hungary/
