Perhaps you should try some spelling variations:
cay tren » chay tren, ca tren, cau tren
sach ky » sac ky, sach y, sach ty
cua cay » cua cac
dan cua » dan ca, ban cua, dai cua
thuc va » thuc vat, thuc dan, thuc day
ve cham » va cham, ve chat, vu cham
tu sach » thu sach, su sach, te sach
nang co » nang doc, nang noi, nang hoc
ve cam » ve cac, va cam, ve cai
va dan » ca dan, va dao, va dau

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 ky ((nang co) or (nang cao)) hoi. hieu ((ve cam) OR (ve cham)) thuc va dan cua cay tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang co) OR (nang cao)) hoi. hieu ((ve cam) OR (ve cham)) thuc va dan cua cay tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang co) or (nang cao)) hoi. hieu ((ve cam) OR (ve cham)) thuc va dan cua cay tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang co) or (nang cao)) hoi. hieu ((ve cam) OR (ve cham)) thuc va dan cua cay tren*.