@incollection{MEM_2022_51_a20,
     author = {Bouyuklieva, Stefka},
     title = {Preface},
     booktitle = {},
     series = {Mathematics and Education in Mathematics},
     pages = {5--6},
     year = {2022},
     volume = {51},
     language = {bg},
     url = {http://geodesic.mathdoc.fr/item/MEM_2022_51_a20/}
}