PRS-350 About the epub custom font path And how to know the path?

I register for this question and my japan version prs-350.

As you know, the japan prs 350 can't be flashed.
So I turn to use epub format to custom font by css.

Though, it's not over.
The problem is I can't find the custom font path in my 350.
I put fonts both in /FONT and /fonts,and add all the paths as follows:

@font-face {
font-family:"zw";
src:url(res:///opt/sony/ebook/FONT/zw.ttf),
url(res:///ebook/fonts/../../ebook/fonts/zw.ttf),
url(res:///ebook/fonts/zw.ttf),
url(res:///Data/FONT/zw.ttf),
url(res:///opt/sony/ebook/FONT/tt0011m_.ttf)
url(res:///fonts/ttf/zw.ttf),
url(res:///../../media/mmcblk0p1/fonts/zw.ttf),
url(res:///DK_System/system/font/zw.ttf),
url(res:///abook/fonts/zw.ttf),
url(res:///system/fonts/zw.ttf),
url(res:///system/media/sdcard/fonts/zw.ttf),
url(res:///sdcard/fonts/zw.ttf),
url(res:///system/fonts/DroidSansFallback.ttf),
url(res:///mnt/MOVIFAT/font/zw.ttf),
url(fonts/zw.ttf);
}

none of them works for me and my japan 350.
I have done a lot search, but no answer.
So, anybody can tell me,
1\What is the right font path used in css?
2\How can I find the right font path used in css?

Any help is welcome, thanks in advance!