Start by naming the Top 10 (incl ties) Goal Leaders for 2000. For 2001, name the Top 10 assuming the 2000 Top 10 had Retired. For 2002, assume those in the 2000 & 2001 lists had retired, and so on.
Basically - for a given year, for a player to be in that list they must be among the top 10 Goal leaders for that year NOT INCLUDING those who would've been listed for a previous year in the quiz. So for 2002, you are looking for players who weren't in the 2000 Top 10, nor those who were in the 2001 Top 10 (a Top 10 which excluded the 2000 Top 10)...and so on. So no player will be listed more than once.