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These typographical errors were made in the manuscript submitted for publication and therefore are not the fault of the publisher. It should be noted that the validity of the result curves given in the paper is not affected. ay )•-(2) In Eq. (5), (d 2 w/dx 2 ) 2 and (d 2 w/dy 2 ) 2 should be replaced by (dw/dx) 2 and (dw/dy) 2 , respectively.(3) In the first term of Eq. (6), the number 16 should be replaced by the number 8.(4) In Eqs. (7) and (8), the quantity [1 -n 2 (3 2 ] 2 should be replaced by the quantity [1 + n 2 (3 2 ] 2 .(5) The factor outside the bracket in Eq. (9) should read 8k bx (3 2 ai/Tr 2 A.(6) Expression (10) should be set equal to zero.(7) In the expression for A following Eq. (10), the first term should read (1 + i 2 P 2 ) 2 .