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The majority (n=12, 70.6%) of studies were published in the last seven years (2012-2018) (25, 26, 28, 30-32, 34-38, 40) and the remaining studies (n=5, 29.4%) were published more than ten years ago (1990-2007) (24, 27, 29, 33, 39). Fifteen studies were published as journal articles, and two were conference abstracts. Four studies originated in the United States, three each from Spain and South Korea, two from each of the following countries, Canada, and Japan, and one each from South Africa, Germany, and Italy. The mean sample size (standard deviation) was 38.1 (34.9) subjects.