Rolf Lengstrand is a Swedish author who produced a set of stories about the Pony Club in Sweden, some in partnership with Pierre L Rolén. Disentangling the books is not particularly easy. I have given an additional list of other books I have found which may well be other titles not translated into English. The vagaries of translation do not mean that this is necessarily the case.
The books came about when a stable was threatened with demolition and the girls who rode there decided to save it through getting books published about the Wahl Pony Club. This series was the result; most illustrated with black and white photographs and featuring Fia. Later books appeared in colour. The information I have found on the books suggests the books were yearbooks. This might be a problem in translation, or simply mean that a book was published each year, but was not a year book in the way we understand it.
A few of the books were translated into English, and read now as period pieces. Although photographic cover illustration became the norm in the UK, the use of photographs to illustrate stories rooted them too much in their time and place. Despite the quality of the photographs, the stilted nature of the stories in translation did not make them popular. The books only had one publication in the UK.
Finding the books
All the books are easy to find.
Links and sources
The history of the Pony Club series (in Swedish)
Bibliography: pony books only
The Long Pony Race, B. Wahlströms Bokförlag AB, Stockholm
Brockhampton Press, Leicester, 1964, trans Marianne Turner
A Knopf, 1966. Photographs Arthur Svenonius. 85 pp.
The Pony Club through Smoke and Fire, B. Wahlströms Bokförlag AB, Stockholm, 1964
Brockhampton Press, Leicester, 1966, trans Marianne Turner, photographs Lennart Blomqvist. 85 pp.
The Long Pony Trek, Brockhampton Press, Leicester, 1964, 84 pp.
A Knopf, 1968
A Horse Astray in Stockholm, Lerner Publications, Minneapolis,1965, photographs Arthur Svenonius, trans Lotte Seidler
A POSSIBLE LIST OF OTHER TITLES
Ponnyklubben och det trettonde hindret
The Pony Club and the Thirteenth Barrier
Ponny-klubben och överfallet på ranchen
The Pony Club and the Attack on the Ranch
Ponnyklubben och hästtjuvarna
The Pony Club and the Castle Mystery
Ponnyklubben och borgens hemlighet
The Pony Club and the Guarantee of Secrecy