Author-date referencing (or the Harvard system or Harvard style of parenthetical referencing) is common in articles published in Wikipedia, though Author-title referencing is also used in articles in Wikipedia; both styles are acceptable citation formats in Wikipedia.nder the author-date referencing system, a book is cited in the text in parentheses, after the section, sentence, or paragraph for which the book was used as a source, using the surname of the author and the year of publication only, with the parentheses closing before the period, as in (Author 2005) .
But John Hughes Benett was the first person to legally discovered leukemia in 1845 in Edinburgh. Later on, in the 19th century, many European scientists found out that there were some people who suffered from abnormal and excess production of white blood cells. They called it as weisses blut that means white blood.
In 1869 Russian chemist Dimitri Mendeleev started the development of the periodic table, arranging chemical elements by atomic mass. He predicted the discovery of other elements, and left spaces open in his periodic table for them.In 1886 French physicist Antoine Bequerel first discovered radioactivity.Thomson student from New Zealand Ernest Rutherford named three types of radiation; alpha, beta and gamma rays.n 1894 Sir William Ramsay and Lord Rayleigh discovered the noble gases, which were added to the periodic table as group 0. In 1897 English physicist J. J. Thomson first discovered electrons; small negatively charged particles in an atom. John Townsend and Robert Millikan determined their exact charge and mass.