A further safety element is constituted by the fact that said markings 10 are embedded in patterns which constitute the normal safety printings or patterns, indicated by 20, so that said markings cannot be easily perceived optically since, although they are present, they constitute {HEAD ~ an integral part} of {TAIL ~ the safety pattern} or printing 
of
A further safety element is constituted by the fact that said markings 10 are embedded in patterns which constitute the normal safety printings or patterns , indicated by 20 , so that said markings can not be easily perceived optically since , although they are present , they constitute { HEAD ~ an integral part } of { TAIL ~ the safety pattern } or printing
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH