WHY To STUDY 



21 



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prri p-ii [7T] p-ri rrsi pn ra [vl [vl [vl Ivl [vl [T:irr:]f:T|fr:|fr:l|:Ti 



! [ [ ! | ] ] | [ [ | [ [ V| [ [ [ *| ! | | ! ! | l ! I* ! ! l ! l | l ! ! 



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HHE1QEIE] HHOHaQQ 000000 



Fig. i. 



