The problem: Answer a question about this article:
A state's consent may be invalidated if there was an erroneous understanding of a fact or situation at the time of conclusion, which formed the "essential basis" of the state's consent. Consent will not be invalidated if the misunderstanding was due to the state's own conduct, or if the truth should have been evident.
What on behalf of a state cannot invalidate that state's consent to a treaty?
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The answer: own conduct

The problem: Answer a question about this article:
As the Ottoman Empire gradually shrank in size, some 79 million Turkish-Muslims from its former territories in the Caucasus, Crimea, Balkans, and the Mediterranean islands migrated to Anatolia and Eastern Thrace. After the Empire lost the Balkan Wars (191213), it lost all its Balkan territories except East Thrace (European Turkey). This resulted in around 400,000 Muslims fleeing with the retreating Ottoman armies (with many dying from cholera brought by the soldiers), and with some 400,000 non-Muslims fleeing territory still under Ottoman rule. Justin McCarthy estimates that during the period 1821 to 1922 several million Muslims died in the Balkans, with the expulsion of a similar number.
What was the sole territory that the empire kept in the Balkans after 1913?
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The answer: East Thrace (European Turkey)

The problem: Answer a question about this article:
Poland has historically been staunchly pro-American, dating back to General Tadeusz Kosciuszko and Casimir Pulaski's involvement in the American Revolution. This pro-American stance was reinforced following favorable American intervention in World War I (leading to the creation of an independent Poland) and the Cold War (culminating in a Polish state independent of Soviet influence). Poland contributed a large force to the "Coalition of the Willing" in Iraq. A quote referring to Poland as "the 51st state" has been attributed to James Pavitt, then Central Intelligence Agency Deputy Director for Operations, especially in connection to extraordinary rendition.
What had been Poland's stance towards the US, historically?
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The answer: staunchly pro-American

The problem: Answer a question about this article:
Tuvalu participates in the work of Secretariat of the Pacific Community, or SPC (sometimes Pacific Community) and is a member of the Pacific Islands Forum, the Commonwealth of Nations and the United Nations. Tuvalu has maintained a mission at the United Nations in New York City since 2000. Tuvalu is a member of the World Bank and the Asian Development Bank. On 18 February 2016 Tuvalu signed the Pacific Islands Development Forum Charter and formally joined the Pacific Islands Development Forum (PIDF).
On what date did Tuvalu join the Pacific Islands Development Forum?
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The answer:
18 February 2016