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http://www6.snunit.k12.il/science/biology/sup1.html
http://www.geocities.com/HotSprings/Bath/6482/Hebrew/plants/hita.html
http://www.edu-negev.gov.il/mad/abuhduba/tobshbat/att1.doc
http://www.oranim.ac.il/marpad/yesod/shavuot/hitata.htm