Context: On 12 March 1999, the Czech Republic, Hungary, and Poland joined NATO; Bulgaria, Estonia, Latvia, Lithuania, Romania, and Slovakia joined in March 2004; Albania joined on 1 April 2009.

Question: Which former Eastern Bloc country was the latest to join NATO?
Answer: Albania

Question: In which year did Poland join NATO?
Answer: 1999

Question: In which year did Slovakia join NATO? 
Answer: 2004

Question: Which countries joined NATO on 12 May 1999?
Answer: Unanswerable

Question: Which countries joined NATO in May 2004?
Answer: Unanswerable

Question: Which country joined NATO on 11 April 2009?
Answer: Unanswerable

Question: Hungary joined which organization in March 2004?
Answer: Unanswerable

Question: Poland joined which organization in March 2004?
Answer: Unanswerable