In the "Fundamentals of the NL Post-Flop game" sample hand 7:
Preflop: Hero is MP1 with Q :diamond:, A :spade:. SB posts a blind of $0.10.
2 folds, UTG+2 calls $0.25, Hero raises to $1.25, 2 folds, Villain (CO) calls $1.25, 3 folds, UTG+2 calls $1.
Flop: ($4.10) 3 :spade:, A :club:, 9 
(3 players)
UTG+2 checks, Hero bets $3, Villain (CO) calls $3, UTG+2 folds.
Turn: ($10.10) 4 
(2 players)
Villain (CO) checks, Hero checks.
Can anyone find it? :P.
How can the CO check before me on the turn? ^^
