[3] Dalton F. E. And Dalton L. C., 2006 Swimming Scientifically Taught A Practical Manual for Young and Old, [EBook #19065], ISO-8859-1, http://manybooks.net/, p.26
[4] Panait L., Duta D., Negrea V., „Experimental approach regarding investigation level of general physical training for tennis players aged 13 to 14 years”, (Ovidius University Annals, Series Physical Education and Sport / Science, Movement And Health, Vol XIII, Issue 2 suppl, 2013, p.284 http://www.analefefs.ro/anale-fefs/2013/s1/pe-autori/29.pdf.