Because of production problem, Figure 1b and Figure 3 lost some of the detail, and we are reprinting the correct figures below.

Fig. 1.

Fig. 3.
On page 683, right hand column, line 17 the following:

should be corrected to:

(e-mail: zw_lu@sohu.com)
Published online by Cambridge University Press: 21 January 2010
Because of production problem, Figure 1b and Figure 3 lost some of the detail, and we are reprinting the correct figures below.
Fig. 1.
Fig. 3.
On page 683, right hand column, line 17 the following:
should be corrected to:
(e-mail: zw_lu@sohu.com)
Fig. 1.
Fig. 3.