Written by - which is lyricist and which is composer?

When a song lists two writers as in the song Slowly, "written by Webb Pierce, Tommy Hill", which person was lyricist and which was composer, or does SHS always list the lyricist before the composer?

When SHS says "Written by", without specifying a composer or an author, they are both credited for the music and the lyrics. If there's an instrumental listed, then you can get the confirmation of the composer(s) known by SHS.