My comment:
(a) "此前，中国社科院副研究员王国乡发帖称，芮成钢涉间谍案，不是一般的严重，可能面临死刑。"
The only posting I can find--and THE one cited by VOA, because other news reports quote the 王国乡's posting, making it possible to identify it--is as follows.
王国乡 has deleted it, from his Sina Weibo. Yet Google keeps a cache:
webcache.googleusercontent.com/search?q=cacheAAYOlqvvSQJ:weibo.com/2707259241/Bm4TcdlWS+&cd=2&hl=en&ct=clnk&gl=us
央視前主播 被指做間諜; 芮成鋼7月被捕 爆料者：不判死難息民憤. 明報, Sept 11, 2014.
news.mingpao.com/20140911/caa1.htm
(ii) The preceding Mingpao report cites
令计划夫妇指使 芮成钢爆习温家族敛财. 博讯, Aug 31, 2014.
boxun.com/cgi-bin/news/gb_display/print_versiOn.cgi?art=/gb/china/2014/08&link=201408310614.shtml
(the last line: “ 来源：苹果日报”)
(iii) 令計劃夫婦指使 向《紐時》彭博社放料; 芮成鋼爆習溫斂財惹禍.
hk.apple.nextmedia.com/international/art/20140831/18850655
(the first clause: “本港新出版時政雜誌《博訊》透露”)
The (ii) and (iii) have the SAME content (except slightly different titles). My guess is 博訊 雜誌 (as opposed to the website Boxun,com) is not published online at all (because I can not find the magazine online). Then on Aug 31 the magazine in Hong Kong published the report, which was republished in large measure by Apple Daily (HK), which Boxun.com in turn re-published.
AAYOlqvvSQJ:weibo.com/2707259241/Bm4TcdlWS+&cd=2&hl=en&ct=clnk&gl=us