Sommaire du Fascicule no. 1

Contents
Cyclicity in a special class of hypergroups
p. 3-6
The set of hypergroups with operators which are constructed from a set with two elements
p. 7-10
Remarks on tolerance algebras
p. 11-16
On a class of subdirectly irreducible groupoids
p. 17-24
A note on subdirectly irreducible groupoids
p. 25-28
On a class of groupoids
p. 29-49
Motion of cometary particle with variable mass under central fields of forces
p. 51-61
Radiation transfer in circumstellar dust envelopes with spherical symmetry - Henyey's method of solution
p. 63-75

Sommaire du Fascicule no. 2

Contents
Homegeneous groupoids
p. [3]
Opérations dérivées des treillis orthomodulaire (Part 1)
p. 7-14
On the extremal points of the closed unit balls in some abstract spaces
p. 15-22
Notes on left distributive groupoids
p. 23-37
Notes on associative triples of elements in commutative groupoids
p. 39-47
Quasitrivial groupoids and balanced identities
p. 49-64
The estimation of the dust content in the atmosphere of comet West 1975n
p. 65-76