Animal Fairy Tales
Two of those books were the last two in his Oz series ( "The Magic of Oz" and "Glinda of Oz" ) , which were published in 1919 and 1920; the third book was "Animal Fairy Tales" . 
<triplet> The Magic of Oz <subj> Oz series <obj> part of the series <subj> Glinda of Oz <obj> followed by <triplet> Glinda of Oz <subj> Oz series <obj> part of the series