Evgenios Avgerinos & Andreas Marinos
On Using a Dynamic Geometry Software in the Comprehension of the Similarity of Triangles

Grozio Stanilov & Slavka Slavova
Models of the Real Projective Plane and Linear Combination of them

Hiroshi Okumura
Generalized Non-Archimedean Twin Circles of the Arbelos

Ivanka Marasheva-Delinova & Emil Delinov
Motivation of Students for Research Work Using Rotation Bodies Geometry

Kliment Vassilev & Donka Pashkuleva
On the Concept of a Quadrilateral in the School Geometry Course

Masayuki Watanabe
Circumscribed and Orthogonal Archimedean Circles in Generalized Arbelos

Sava Grozdev & Toni Chehlarova
Congruences in Triangular Nets

Stavroula Patsiomitou & Anastassios Emvalotis
Developing Geometric Thinking Skills Through Dynamic Diagram Transformations

Toni Chehlarova & Evgenia Sendova
Explorations with Rotational Solids