Perhaps you should try some spelling variations:
tang mai » tang ma, tang tai, sang mai
ban hanh » ban hang
lang mai » lang dai, lang hai, lang man
cam tuc » cam xuc, cam tu, nam thuc
vai cua » dai cua, hai cua, lai cua
tuc ban » thuc ban, truc ban, tu ban
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
va cam » va cham, va cac, va cao
sach 6 » sach y, sach 2
vi cua » di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach 6 ((tang mai) OR (lang mai)) hoi. hieu va cam tuc ban hanh ((vi cua) or (vai cua)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach 6 ((tang mai) OR (lang mai)) hoi. hieu va cam tuc ban hanh ((vi cua) OR (vai cua)) viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach 6 ((tang mai) OR (lang mai)) hoi. hieu va cam tuc ban hanh ((vi cua) or (vai cua)) viet*".