His first work was published in 1993 under the title Ich will kein inmich mehr sein: Botschaften aus einem autistischen Kerker (I Don't Want to Be Inside Me Anymore: Messages from an Autistic Mind, lit. transl. "an inside-me") and was soon translated into languages worldwide. Sellin has been a contributing author to other publications since then. He became the centre of an often volatile controversy about the use of facilitated communication as a valid form of communication for functionally non-verbal people with autism. In 2010, Orlai Produkciós Iroda made a monodrama, Nemsenkilény, monológ nemmindegyembereknek ("Notanobodycreature"), from the book by Henriett Seth F. The script contains excerpts from Donna Williams' Nobody Nowhere: The extraordinary Autobiography of an Autistic Girl, Sellin's I Don't want to Be Inside Me Anymore, and Mark Haddon's The Curious Incident of the Dog in the Night-time.
This supported form of typed communication had been already used for years by some people in the Cerebral Palsy population with severely impaired speech, but was considered invalid when used by functionally non-verbal people with autism on the basis that functionally non-verbal people in the autistic population were generally assumed to be mentally retarded, so profound writings by such people were considered impossible. Since the more recent publication of works by other functionally non-verbal authors with autism who progressed from facilitated communication to independent typing, the technique is beginning to be more widely accepted for this group. In this sense, Birger was a pioneer who braved the publication of his typed communication and in doing so paved the way for later functionally non-verbal authors with autism worldwide.