Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
nang mai » nang ma, nang tai, lang mai
thuc dan » thuc hanh, hoc dan, thuc vat
sach ty » sach y, sach tu, sach thu
thuc va » thuc vat, thuc day
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
ty nang » ky nang, ty xang, ty hang
va cam » va cham, va cac, va cai
dan di » danh di, dan da, dan de
di cau » da cau, diem cau
va cao » va cac, va co, va dao

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 ty nang mai hoi. hieu ((va cam) or (va cao)) ((thuc va) or (thuc dan)) dan di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang mai hoi. hieu ((va cam) OR (va cao)) ((thuc va) OR (thuc dan)) dan di cau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang mai hoi. hieu ((va cam) or (va cao)) ((thuc va) or (thuc dan)) dan di cau tren*.