Umthwalo ohamba ngezinyawo wasungulwa nini?
Umthwalo ogingqikayo wasungulwa nguBernard D. Sadow ngo-1970. Ukusungula kwakhe kwachazwa nge-patent, enenombolo ethi 3,653,474, eyayigcizelela ukukhula kokuhamba ngendiza njengendlela yokusebenzisa ekhuthazayo. Isikhuthazo sokunamathisela amasondo ngqo emithwalweni kwaba ukubonwa nguSadow womthwali wokubeka imithwalo enqoleni enamasondo.