no. 1
On the periodicity of morphisms on free monoids
RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications, Tome 20 (1986) no. 1, pp. 47-54. 
@article{ITA_1986__20_1_47_0,
     author = {Harju, Tero and Linna, Matti},
     title = {On the periodicity of morphisms on free monoids},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {47--54},
     publisher = {AFCET - Gauthier-Villars},
     address = {Paris},
     volume = {20},
     number = {1},
     year = {1986},
     mrnumber = {849965},
     zbl = {0608.68065},
     language = {en},
     url = {http://archive.numdam.org/item/ITA_1986__20_1_47_0/}
}
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AU  - Linna, Matti
TI  - On the periodicity of morphisms on free monoids
JO  - RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications
PY  - 1986
SP  - 47
EP  - 54
VL  - 20
IS  - 1
PB  - AFCET - Gauthier-Villars
PP  - Paris
UR  - http://archive.numdam.org/item/ITA_1986__20_1_47_0/
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%A Linna, Matti
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%D 1986
%P 47-54
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Harju, Tero; Linna, Matti. On the periodicity of morphisms on free monoids. RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications, Tome 20 (1986) no. 1, pp. 47-54. http://archive.numdam.org/item/ITA_1986__20_1_47_0/

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