Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nang ma » tang ma, sang ma, nang cao
hieu va » hieu qua
va hanh » van hanh, va thanh, va danh
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
ma hoi » mai hoi, xa hoi, ma hoa
xuc va » duc va, tuc va, luc va
dai va » mai va
di va » di vao, doi va, di vat
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach v nang ma hoi. ((hieu va) or (lieu va)) cam xuc va hanh ((di va) OR (dai va)) thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach v nang ma hoi. ((hieu va) OR (lieu va)) cam xuc va hanh ((di va) OR (dai va)) thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach v nang ma hoi. ((hieu va) or (lieu va)) cam xuc va hanh ((di va) OR (dai va)) thiet".
• Adding a wildcard symbol may retrieve word variants: toc sach v nang ma hoi. ((hieu va) or (lieu va)) cam xuc va hanh ((di va) OR (dai va)) thiet*.