cho tới nay 
until now [ cho ] : add, give; to, for; to say, claim; in order to; let, allow, permit
[ tới ] : to come, arrive, reach; until, to; next
[ nay ] : (1) this, these; (2) today, at present, nowadays, now, at this time
Most Common Compounds Set 1:
Most Common Compounds Set 2 :