1*. -i3._ ,2. 



aoA *^\^ *^2^ ♦a'i^<a4 . 



s = 3 2 — t • ^" ^P. 



b^ ♦b2A ♦by^ 



^'^^^*^^'-"^2^^^-2^^2''oi-Vl^-'"2^vv2^^*[^^^t'^^V4^^^''^^42«3-'V4>^''2-2^''3^'3-'<''l''2-='v3^'2^3]•°' 



♦ /-a b2+a b b -db2 

 - V 42323 3 



^ IV "*o' 



,b3tcb3bj^-a4b-^ ^ 



T3 = ♦y.db^.a^b^bg-apb^ , 



with signs chosen so that 

 biTi*b2T2*b3T3= ^ 



"3 V"i"V • 



c 



