Impact of pay-for-performance on work motivation of sales personnel : a case of information media firmsTepp, Milvi; Poomann, MonikaWorking papers in economics. Vol. 19 (TUTWPE No 141-144)2006 / TUTWPE No. 144, p. 79-90 : illhttps://artiklid.elnet.ee/record=b1020692*est