Table:
text: 1963 International Gold Cup
Results
Results
Pos Driver Entrant Constructor_ Time_Retired Grid_
1 Jim Clark Team Lotus Lotus-Climax 2.02:58.6 1
2 Richie Ginther Owen Racing Organisation BRM + 22.6 s 3
3 Graham Hill Owen Racing Organisation BRM + 28.2 s 2
4 Jack Brabham Brabham Racing Organisation Brabham-Climax + 52.0 s 11
5 Tony Maggs Cooper Car Company Cooper-Climax 72 laps 6
6 Bruce McLaren Cooper Cooper-Climax 72 laps 7
7 Mike Hailwood Reg Parnell (Racing) Lola-Climax 70 laps 9
8 Ian Burgess Scirocco-Powell (Racing Cars) Scirocco-BRM 69 laps 18
9 Peter Revson Reg Parnell (Racing) Lotus-BRM 69 laps 15
10 Carel Godin de Beaufort Ecurie Maarsbergen Porsche 67 laps 20

text: 1963 International Gold Cup
Results
Results
Pos Driver Entrant Constructor_ Time_Retired Grid_
11 Jo Siffert Siffert Racing Team Lotus-BRM Engine (66 laps) 12
12 André Pilette André Pilette Lotus-Climax 63 laps 21
13 Innes Ireland British Racing Partnership Lotus-BRM Oil pressure (56 laps) 5
14 Bernard Collomb Bernard Collomb Lotus-Climax Oil pressure (46 laps) 19
Ret Ian Raby Ian Raby (Racing) Gilby-BRM Ignition 13
Ret Dan Gurney Brabham Racing Organisation Brabham-Climax Oil leak 16
Ret Mike Beckwith British Racing Partnership Lotus-BRM Accident 17
Ret Masten Gregory Tim Parnell Lotus-BRM Cam follower 14
Ret Trevor Taylor Team Lotus Lotus-Climax Crownwheel & pinion 4
Ret Jo Bonnier Rob Walker Racing Team Cooper-Climax Oil pressure 8
Ret Tony Settember Scirocco-Powell (Racing Cars) Scirocco-BRM Valve gear 22

text: 1963 International Gold Cup
Results
Results
Pos Driver Entrant Constructor_ Time_Retired Grid_
Ret Bob Anderson DW Racing Enterprises Lola-Climax Gearbox 10
WD Peter Arundell Team Lotus Lotus-Climax Car not ready -

Question: How many different drivers are listed in the 1963 International Gold Cup?