Hard to tell after wiping …_篮球即时比分_nba比分直播-彩客网重点推荐

sgml
2012-09-26T14:56:53.000Z
type:structured-message
www.uio.no

Hard to tell after wiping the board, but:

I might have written that volume was sum of the areas. Should be sum of (area * slice thickness). Slice thickness Δr tends to dr.