Hauv txhua qhov kev tswj hwm thiab vaj tse thiab cov txheej txheem sib koom ua ke uas tshwm sim txhua hnub hauv lub neej, xws li cov ntaub ntawv xws li phau ntawv hauv tsev yog koom ncaj qha. Nws yog ntau dua ntawm cov tswv ntawm cov tsev ntiag tug, txawm li cas los xij, cov tswv ntawm cov chav tsev zoo tib yam kuj ntsib nws. Yog li ntawd, nws yog ib qho tseem ceeb kom paub lub luag haujlwm tseem ceeb ntawm daim ntawv no, nrog rau me ntsis ntawm nws keeb kwm