(;
AB[br][cr][bq][cp][fp][pp][do][eo]
AW[dr][cq][dq][eq][gq][hq][kq][bo][en][cm][cj]
C[Black plays.

Source:
     Tesuji Dictionary, by Segoe Kensaku & Go Seigen]
(;
B[bp]
C[Hopefully, no one would chose to connect here.  Black does connect out with the corner stones, but ...];
W[co]
C[... White eliminates a weakness, while forcing Black to connect again on a dame point.];
B[dp];W[fn]
C[White uses sente to force Black into terrible shape.  With only one eye in the corner, Black has bleak prospects for a 2nd eye or escaping.]
)
    (;
    B[bn]
    C[The tesuji to connect.];
    W[cn]
    C[White can easily capture the stone, but ...];
    B[co];W[bm];B[bp]
    C[... Black connects in sente.]
    (;
    W[fn];B[ao]
    C[Now taking the vital outside point isn't catastrophic, because Black can live with 7 or so points.]
    )
        (;
        W[an];B[fn]
        C[With one eye in the corner, Black takes the vital outside point.  Black's prospects are significantly better than connecting without the sacrifice tesuji.]
        )
    )
)

