Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
cau tren » dau tren, ca tren, cau treo
sach ky » sac ky, sach y, sach ty
cu tren » tu tren, dua tren
cao hoi » cau hoi, co hoi, cao hoc
ve cap » ve cac, ve cai, ve cau
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va
le cap » le cau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ky nang cao hoi. hieu ((ve cap) or (le cap)) nuoc va dan vi ((cau tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky nang cao hoi. hieu ((ve cap) OR (le cap)) nuoc va dan vi ((cau tren) OR (cu tren)).
• Adding a wildcard symbol may retrieve word variants: doc sach ky nang cao hoi. hieu ((ve cap) or (le cap)) nuoc va dan vi ((cau tren) or (cu tren))*.