June 21 » Boxer Rebellion. China formally declares war on the United States, Britain, Germany, France and Japan, as an edict issued from the Empress Dowager Cixi.
July 19 » The first line of the Paris Métro opens for operation.
July 29 » In Italy, King Umberto I of Italy is assassinated by the anarchist Gaetano Bresci.
December 14 » Quantum mechanics: Max Planck presents a theoretical derivation of his black-body radiation law.
December 18 » The Upper Ferntree Gully to Gembrook, Victoria Narrow-gauge (2ft 6 in or 762mm) Railway (now the Puffing Billy Railway) in Victoria, Australia is opened for traffic.
December 19 » Hopetoun Blunder: The first Governor-General of Australia John Hope, 7th Earl of Hopetoun, appoints Sir William Lyne premier of the new state of New South Wales, but he is unable to persuade other colonial politicians to join his government and is forced to resign.
Day of death April 20, 1955
The temperature on April 20, 1955 was between 3.2 °C and 11.3 °C and averaged 6.5 °C. There was 7.0 hours of sunshine (49%). The partly or heavily clouded was. The average windspeed was 3 Bft (moderate breeze) and was prevailing from the northwest. Source: KNMI
April 12 » The polio vaccine, developed by Dr. Jonas Salk, is declared safe and effective.
May 14 » Cold War: Eight Communist bloc countries, including the Soviet Union, sign a mutual defense treaty called the Warsaw Pact.
May 18 » Operation Passage to Freedom, the evacuation of 310,000 Vietnamese civilians, soldiers and non-Vietnamese members of the French Army from communist North Vietnam to South Vietnam following the end of the First Indochina War, ends.
September 6 » Istanbul's Greek, Jewish, and Armenian minorities are the target of a government-sponsored pogrom; dozens are killed in ensuing riots.
October 26 » After the last Allied troops have left the country, and following the provisions of the Austrian Independence Treaty, Austria declares that it will never join a military alliance.
November 5 » After being destroyed in World War II, the rebuilt Vienna State Opera reopens with a performance of Beethoven's Fidelio.
When copying data from this family tree, please include a reference to the origin: Joop Klavers, "Family tree Klavers", database, Genealogy Online (https://www.genealogieonline.nl/stamboom_klavers/I314992.php : accessed March 1, 2026), "Jacob Mook (± 1875-1955)".
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