In general these guidelines apply: Codes B20 through B29 cover lines after 1.e4 c5 where White does not play 2.Nf3, and lines where White plays 2.Nf3 and Black responds with a move other than 2...d6, 2...Nc6 or 2...e6.
In general these guidelines apply: Kode B20 sampai B29 berisi jalur setelah 1.e4 c5 dimana Putih tidak memainkan 2.Nf3, dan jalur dimana Putih memainkan 2.Nf3 dan Hitam membalas dengan gerakan selain 2...d6, 2...Nc6 or 2...e6.