2007, p. 224 1 2 Frobisher 1999, p. 41 ↑ This is the timeframe in United States, Canada, Great Britain, Australia, and Israel; see Levenson, Tsamir & Tirosh (2007, p. 85). ↑ Frobisher 1999, pp. 31 (Introduction); 40–41 (The number zero); 48 (Implications for teaching) ↑ Frobisher 1999, pp. 37, 40, 42; results are from the survey conducted in the mid-summer term of 1992. ↑ Frobisher 1999, p. 41 "The percentage of Year 2 children deciding that zero is an even number is much lower than in the previous study, 32 per cent as opposed to 45 per cent" ↑ Frobisher 1999, p. 41 "The success in deciding that zero is an even number did not continue to rise with age, with approximately one in two children in each of Years 2 to 6 putting a tick in the 'evens' box ..." ↑ Frobisher 1999, pp. 40–42, 47; these results are from the February 1999 study, including 481 children, from three schools at a variety of attainment levels. ↑ Frobisher 1999, p. 41, attributed to "Jonathan" ↑ Frobisher 1999, p. 41, attributed to "Joseph" ↑ Frobisher 1999, p. 41, attributed to "Richard" ↑ Keith 2006, pp. 35–68 "There was little disagreement on the idea of zero being an even number.