希尔伯特第十四问题 hilbert's fourteenth problem

四问青歌赛 Northern Music

四色问题 four color problem ; Four-color problem

四肢问题 Trouble on limbs

十四的质问 Chapter Sixty Six

四种疑问句 Four Kind of Question

四处询问 ask around ; Around asking

四阶边值问题 fourth-order boundary value problem ; fourth-order bvp

存在四个问题 There are four problems ; Exist four issues ; There are four issues

四色方柱问题 Instant Insanity