** April 20 ( Eastern Orthodox liturgics )

** Series two: 13 episodes of 30 minutes broadcast between 19 February 1969 to 14 May 1969, Wednesdays at 17: 20.

** February 20 ( Eastern Orthodox liturgics )

** Pluviôse ( from Latin pluvius, " rainy "), starting 20, 21 or 22 January

** Ventôse ( from Latin ventosus, " windy "), starting 19, 20 or 21 February

** Germinal ( from Latin germen, " germination "), starting 20 or 21 March

** Floréal ( from Latin flos, " flower "), starting 20 or 21 April

** Prairial ( from French prairie, " pasture "), starting 20 or 21 May

** Messidor ( from Latin messis, " harvest "), starting 19 or 20 June

** Thermidor ( or Fervidor ) ( from Greek thermon, " summer heat "), starting 19 or 20 July

** Mk 20 Rockeye II

** 4 × 20 millimetre ( 0. 79 in ) M2 cannon

** Start: July 20, 1966, 23: 01: 00 UTC

** End: July 20, 1966, 23: 40: 00 UTC

** agriculture 20 %

** NATO HQ – Sarajevo, from 2004 ( Bosnia and Herzegovina ) – 20 out of 81 officers from 16 countries

** i386EX: 16 MHz @ 2. 7 ~ 3. 3 volt or 20 MHz @ 3. 0 ~ 3. 6 volt or 25 MHz @ 4. 5 ~ 5. 5 volt

** i386EXTB: 20 MHz @ 2. 7 ~ 3. 6 volt or 25 MHz @ 3. 0 ~ 3. 6 volt

** July 20 ( Eastern Orthodox liturgics )

** June 20 ( Eastern Orthodox liturgics )

** Timkat, or 20 during Leap Year ( Ethiopian Orthodox )

** January 20 ( Eastern Orthodox liturgics )

** LBP5. 000 ($ 3. 50 ) LP30. 000 ($ 20 )

** 2 × 20 mm Type 99 cannon in the wings, with 60 rounds per gun.

** Earliest day on which Feast of the Immaculate Heart of Mary can fall, while July 3 is the latest ; celebrated 20 days after Pentecost.

** Eunectes murinus, the green anaconda, the largest species, is found east of the Andes in Colombia, Venezuela, the Guianas, Ecuador, Peru, Bolivia, Brazil and on the island of Trinidad.

** Eunectes notaeus, the yellow anaconda, a smaller species, is found in eastern Bolivia, southern Brazil, Paraguay and northeastern Argentina.

** Eunectes deschauenseei, the dark-spotted anaconda, is a rare species found in northeastern Brazil and coastal French Guiana.

** Eunectes beniensis, the Bolivian anaconda, the most recently defined species, is found in the Departments of Beni and Pando in Bolivia.

** Well-ordering theorem: Every set can be well-ordered.

** Tarski's theorem: For every infinite set A, there is a bijective map between the sets A and A × A.

** Trichotomy: If two sets are given, then either they have the same cardinality, or one has a smaller cardinality than the other.

** The Cartesian product of any family of nonempty sets is nonempty.

** König's theorem: Colloquially, the sum of a sequence of cardinals is strictly less than the product of a sequence of larger cardinals.

** Every surjective function has a right inverse.

** Zorn's lemma: Every non-empty partially ordered set in which every chain ( i. e. totally ordered subset ) has an upper bound contains at least one maximal element.

** Hausdorff maximal principle: In any partially ordered set, every totally ordered subset is contained in a maximal totally ordered subset.

** Tukey's lemma: Every non-empty collection of finite character has a maximal element with respect to inclusion.

** Antichain principle: Every partially ordered set has a maximal antichain.

** Every vector space has a basis.

** Every unital ring other than the trivial ring contains a maximal ideal.

** For every non-empty set S there is a binary operation defined on S that makes it a group.

** The closed unit ball of the dual of a normed vector space over the reals has an extreme point.

** Tychonoff's theorem stating that every product of compact topological spaces is compact.

** In the product topology, the closure of a product of subsets is equal to the product of the closures.

** If S is a set of sentences of first-order logic and B is a consistent subset of S, then B is included in a set that is maximal among consistent subsets of S. The special case where S is the set of all first-order sentences in a given signature is weaker, equivalent to the Boolean prime ideal theorem ; see the section " Weaker forms " below.

** Any union of countably many countable sets is itself countable.