The complement of a graph G is denoted by G. χ(G) denotes the chromatic number and ω(G) the clique number of G. The cycles of odd length at least five are called odd holes and the complements of odd holes are called odd anti-holes. A graph G is called perfect if, for each induced subgraph G of G, χ(G) = ω(G). Classical examples of perfect graphs consist of bipartite graphs, chordal graphs and c...

Optic disc drusen (ODD) are benign congenital anomalies of the optic nerve characterized by calcified hyaline bodies. While superficial drusen can be diagnosed easily during fundus examination, detecting buried drusen requires the use of additional imaging methods such as B-scan ultrasonography (USG), fundus fluorescein angiography (FFA), computed tomography (CT) and fundus autofluorescence (FA...

One can prove the following propositions: (1) For every non zero natural number n holds n − 1 is a natural number and 1 ≤ n. (2) For every odd natural number n holds n − 1 is a natural number and 1 ≤ n. (3) For all odd integers n, m such that n < m holds n ≤ m − 2. (4) For all odd integers n, m such that m < n holds m + 2 ≤ n. (5) For every odd natural number n such that 1 6= n there exists an ...