Please list the first name of the players from the NBA league with the forward position.
"NBA" is the lgID; with the forward position refers to pos = 'F' of pos = 'F-C'
SELECT DISTINCT T1.firstName FROM players AS T1 INNER JOIN players_teams AS T2 ON T1.playerID = T2.playerID WHERE (T1.pos = 'F' OR T1.pos = 'F-C') AND T2.lgID = 'NBA'