Perhaps you should try some spelling variations:
thanh trinh » hanh trinh, thanh tinh, thanh binh
cau tren » cu tren, dau tren, ca tren
dua tren » dung tren
hieu van » hieu va, thien van, lieu va
sach ty » sach y, sach tu, sach thu
so sach » so sanh, bo sach, co sach
nang xa » nang x, lang xa, nang ma
ty nang » ky nang, ty xang, ty hang
luc va » duc va, tuc va, loc va
xuc va » duc va, tuc va, xac va

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ty nang xa hoi. hieu van dao ((xuc va) OR (luc va)) thanh trinh ((dua tren) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty nang xa hoi. hieu van dao ((xuc va) OR (luc va)) thanh trinh ((dua tren) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty nang xa hoi. hieu van dao ((xuc va) OR (luc va)) thanh trinh ((dua tren) or (cau tren))".
• Adding a wildcard symbol may retrieve word variants: so sach ty nang xa hoi. hieu van dao ((xuc va) OR (luc va)) thanh trinh ((dua tren) or (cau tren))*.