@misc {MATHEDUC.02452030,
    author       = {Vinner, S.},
    title        = {The concept of exponentiation of the undergraduate level and the definitional approach.},
    howpublished = {Educat. Stud. Math. (Apr 1977) v. 8(1) p. 17-26.},
    year         = {1977},
    identifier   = {1978b.00649},
}