Perhaps you should try some spelling variations:
cau tren » dau tren, ca tren, cau treo
nang doc » nang luc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
nang co » nang cao, nang noi, nang hoc
cu tren » tu tren, dua tren
ve cam » ve cham, ve cac, va cam
xuc va » duc va, tuc va, luc va
va dan » ca dan, va dao, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky ((nang co) or (nang doc)) hoi. hieu ve cam xuc va dan ca ((cau tren) OR (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang co) OR (nang doc)) hoi. hieu ve cam xuc va dan ca ((cau tren) OR (cu tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang co) or (nang doc)) hoi. hieu ve cam xuc va dan ca ((cau tren) OR (cu tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang co) or (nang doc)) hoi. hieu ve cam xuc va dan ca ((cau tren) OR (cu tren))*.