Collins Chinese Dictionary Plus (3rd edition), 2011:
力争(爭) lìzhēng 动
1
(=极力争取) strive;
(pt strove)(pp striven)力争(爭)上游(遊)
lìzhēng shàngyóu strive for progress
(pt strove)(pp striven)
2
(=极力争辩) argue据(據)理力争(爭)
jù lǐ lìzhēng argue on good grounds