Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
nang mai » nang ma, nang tai, lang mai
hieu su » hieu sau, tieu su, hieu so
va hanh » van hanh, va thanh, ban hanh
va danh » va dinh, va dan, dia danh
cham so » cham soc, cham o, ham so
hieu vu » hieu va, hieu ve, dieu vu
mai hoi » mai khoi, dai hoi, lai hoi
cuu tre » cua tre, cau tren, cau treo
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
di cuu » di cau, di cua, dinh cuu

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 v nang mai hoi. ((hieu vu) or (hieu su)) cham so ((va danh) OR (va hanh)) di cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach v nang mai hoi. ((hieu vu) OR (hieu su)) cham so ((va danh) OR (va hanh)) di cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach v nang mai hoi. ((hieu vu) or (hieu su)) cham so ((va danh) OR (va hanh)) di cuu tre".
• Adding a wildcard symbol may retrieve word variants: doc sach v nang mai hoi. ((hieu vu) or (hieu su)) cham so ((va danh) OR (va hanh)) di cuu tre*.