[1] His first book was Essays; fremmede forfattere from 1895, a collection of articles published in Dagbladet and Kringsjaa.

[2] The performance at the National Theatre in Oslo (premièred on 29 January 1914) was produced by Gustav Thomassen, and saw Johanne Dybwad playing the character "Lavinia" and David Knudsen as the politician "Celius".

[2] Kjær wrote travel letters and participated in public debates, as well as reviewing literature and theatre.

He delivered articles to the newspapers Morgenbladet and Verdens Gang, he was a theatre critic for Aftenposten from 1909 to 1921, and wrote for Tidens Tegn from 1922.

[2] In an obituary in the periodical Samtiden 1924, Sigurd Hoel characterized Kjær as being more critical and analytical than creative, and having more talent for ridicule than for enthusiasm.