Errata
In Eq. (26),
x
~
s
=
x
s
⁄
a
x
,
y
~
s
=
y
s
⁄
a
y
. Corrected by Tao Zhuang.
In Eqs. (27), (28), and (31)
A
m
i
,
A
n
i
,
B
m
i
cos
2
θ
x
,
B
n
i
cos
2
θ
y
should be revised as
A
m
i
⁄
cos
θ
x
,
A
n
i
⁄
cos
θ
y
,
B
m
i
,
B
n
i
, respectively. Corrected by Tao Zhuang.