Quark
The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964. Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until deep inelastic scattering experiments at the Stanford Linear Accelerator Center in 1968. Accelerator experiments have provided evidence for all six flavors. The top quark, first observed at Fermilab in 1995, was the last to be discovered.
Quack-monument
The Quack monument was originally founded in 1926 from a legacy of Arnoldus Burchard Adolphus Quack (Nijmegen, 6 April 1842 - Nijmegen, 11 November 1920). Quack was alderman of the municipality of Nijmegen from 1902 to 1919. The monument is named after him and his twin sister Maria (Marie) Christina (Nijmegen, April 6, 1842 - Nijmegen, March 15, 1905). Quack left his legacy to the municipality of Nijmegen under the condition that a fountain, the Marie Adolphron named after his sister, would be erected.