


[1+a_{xx}x^{2}+a_{xy}xy+a_{yy}y^{2}]^{β} 
 
 

βI_{0}x^{2}[1+a_{xx}x^{2}+a_{xy}xy+a_{yy}y^{2}]^{β1} 
 
 

βI_{0}xy[1+a_{xx}x^{2}+a_{xy}xy+a_{yy}y^{2}]^{β1} 
 
 

βI_{0}y^{2}[1+a_{xx}x^{2}+a_{xy}xy+a_{yy}y^{2}]^{β1} 
 
 

I_{0}[1+a_{xx}x^{2}+a_{xy}xy+a_{yy}y^{2}]^{β}.ln[1+a_{xx}x^{2}+a_{xy}xy+a_{yy}y^{2}] 
 