in this paper we prove that each element of any regular baer ring is a sum of two units if no factor ring of r is isomorphic to z_2 and we characterize regular baer rings with unit sum numbers $omega$ and $infty$. then as an application, we discuss the unit sum number of some classes of group rings.

The identification of species present in an ecosystem and the assessment a faunistic inventory is first step any ecological survey conservation effort. Thanks to technological progress, DNA barcoding has sped up great support morphological taxonomy. In this work, we used “Reverse Taxonomy” approach, where molecular (DNA barcoding) analyses were followed by (skeletal features) ones determine spe...

An echinoderm fauna from the San Salvatore Formation (Middle Triassic, Southern Alps) is here described in detail for first time. Identifiable crinoids and echinoids were collected three different localities: Mt. (Ticino, Switzerland), Rasa di Varese Michele (Lombardy, Italy). Crinoid taxa include Encrinus cf. aculeatus, Holocrinus sp. indet., Zardinicrinus granulosus, Encrinidae gen. et indet....