Her birthday was on July 22nd.

She was nominated for the Hans Christian Andersen Award in 1970.

https://www.wob.com/en-us/books/author/oili-tanninen

"Oili Tanninen is one of Finland's most treasured creators of children's literature. Having written and illustrated over twenty children's books, Tanninen became a household name in the 1960's when her beloved Nunnu books were broadcast as an animation series for television. She has received several major awards throughout her career including the Hans Christen Andersen Certificate of Honour (three times over), the Topelius Finnish Literature Prize, The Rudolf Koiru Award, the State Literature Award, Finland, and most recently, the Kieku Award for lifetime achievement in illustration. Oili Tanninen was born in 1933 in Sortavaia, Finland, and graduated from the Institute of Industrial Arts in 1953. An artist and teacher in the arts, Tanninen and her family lived in Moscow, London and Washington before returning to Helsinki where she now lives."

http://images.google.com/images?gbv=2&hl=en&q=%22oili+tanninen%22&btnG=Search+Images
(photos, some artwork)

http://www.museo24.fi/?action%5B%5D=INavigation::viewArticle(6427)
(in Finnish - includes her 20 titles, written between 1961 and 1991)

http://fi.wikipedia.org/wiki/Oili_Tanninen
(in Finnish)

Translation (first half):

Oili Tanninen (née Nikitin;[1] b. July 22, 1933 in Sortavala[2]) is a Finnish children's writer, printmaker, creator and illustrator of animated films.

Tanninen graduated from the Academy of Arts and Crafts in 1953 and worked twice as an artist in the art industry department of Arabia factories. He has also taught ceramics, porcelain painting and fabric printing at civic and labor colleges.[2]

In 1961, Tanninen published his first children's book Miiru goes fishing. He has also illustrated both his own and other texts. Tanninen has also made animation series for Yleisradio, including the 12-part Miiru and Nunnu series.[2] His children's books have also been translated into German and Japanese.

At the initiative of Raili Rusto, Tanninen made the black-and-white animation series Miiru (1964), Nunnu (1967) and Hissu (1970) for Yleisradio based on his own books. Miiru and Nunnu had ten parts, but Hissu, intended as a Christmas calendar series, has 24 parts. In addition, he made two color Robotti Romulus animations based on his Nappi and Neppari characters in 1974.[3]

Tanninen was married to journalist Aarne Tanninen from 1957[4] until his death. They lived abroad for 24 years, first in Moscow from 1958 and later in London and Washington. After returning to Finland, they have lived in Kruununhaa, Helsinki.[2] Their daughter Maija Tanninen-Mattila is the director of the Helsinki Art Museum.[5]

https://www.kirkusreviews.com/book-reviews/oili-tanninen/button-and-popper/
(Kirkus review of "Botton and Popper")

https://www.goodreads.com/author/list/3372079.Oili_Tanninen
(reader reviews)

https://www.google.com/search?sca_esv=557502889&q=oili+tanninen&tbm=vid&source=lnms&sa=X&ved=2ahUKEwjPzMHf8uGAAxXpjYkEHed-AB4Q0pQJegQIDBAB&biw=1281&bih=816&dpr=1
(videos)