If even the official rules aren't good enough for your friend, how about some actual games played by GMs? For example, check out the last round of the recent FIDE championship; the games can be found at http://chessbase.com/news/2005/sanluis/games/wcch14.htm and probably numerous other places.
In these four games, I count three moves of the type in question: 6. dxc3 in Svidler-Anand, 25. bxc3 in Leko-Kasimjanov, and 50... hxg6 in Morozevich-Adams.
If your friend considers every word on the Internet to be inherently untrustworthy, you might try the local library. Just about any book on chess should contain either the rules or records of games, and you won't have to dig through very many games before finding examples.
In these four games, I count three moves of the type in question: 6. dxc3 in Svidler-Anand, 25. bxc3 in Leko-Kasimjanov, and 50... hxg6 in Morozevich-Adams.
If your friend considers every word on the Internet to be inherently untrustworthy, you might try the local library. Just about any book on chess should contain either the rules or records of games, and you won't have to dig through very many games before finding examples.