The problem: Answer a question about this article:
Ancient tables provided the sun's mean longitude. Christopher Clavius, the architect of the Gregorian calendar, noted that the tables agreed neither on the time when the sun passed through the vernal equinox nor on the length of the mean tropical year. Tycho Brahe also noticed discrepancies. The Gregorian leap year rule (97 leap years in 400 years) was put forward by Petrus Pitatus of Verona in 1560. He noted that it is consistent with the tropical year of the Alfonsine tables and with the mean tropical year of Copernicus (De revolutionibus) and Reinhold (Prutenic tables). The three mean tropical years in Babylonian sexagesimals as the excess over 365 days (the way they would have been extracted from the tables of mean longitude) were 14,33,9,57 (Alphonsine), 14,33,11,12 (Copernicus) and 14,33,9,24 (Reinhold). All values are the same to two places (14:33) and this is also the mean length of the Gregorian year. Thus Pitatus' solution would have commended itself to the astronomers.
What is the theory about leap year called?
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The answer: Gregorian leap year rule


The problem: Answer a question about this article:
There are nevertheless a number of contemporary hunter-gatherer peoples who, after contact with other societies, continue their ways of life with very little external influence. One such group is the Pila Nguru (Spinifex people) of Western Australia, whose habitat in the Great Victoria Desert has proved unsuitable for European agriculture (and even pastoralism).[citation needed] Another are the Sentinelese of the Andaman Islands in the Indian Ocean, who live on North Sentinel Island and to date have maintained their independent existence, repelling attempts to engage with and contact them.[citation needed]
What is the name of the Spinifex people?
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The answer: Pila Nguru


The problem: Answer a question about this article:
During Vatican II, the Council Fathers avoided statements which might anger Christians of other faiths.[page needed] Cardinal Augustin Bea, the President of the Christian Unity Secretariat, always had the full support of Paul VI in his attempts to ensure that the Council language was friendly and open to the sensitivities of Protestant and Orthodox Churches, whom he had invited to all sessions at the request of Pope John XXIII. Bea also was strongly involved in the passage of Nostra aetate, which regulates the Church's relations with the Jewish faith and members of other religions.[d]
Who was President of the Christian Unity Secretariat?
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The answer: Cardinal Augustin Bea


The problem: Answer a question about this article:
Articles 46–53 of the Vienna Convention on the Law of Treaties set out the only ways that treaties can be invalidated—considered unenforceable and void under international law. A treaty will be invalidated due to either the circumstances by which a state party joined the treaty, or due to the content of the treaty itself. Invalidation is separate from withdrawal, suspension, or termination (addressed above), which all involve an alteration in the consent of the parties of a previously valid treaty rather than the invalidation of that consent in the first place.
Which processes simply alter the consent given by parties to a previously valid treaty rather than invalidating the consent completely?
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The answer:
withdrawal, suspension, or termination