NOTATION

o a constant is effective if it can be computed in a finite number of steps

from starting data;

o C(Ai, A2,...) or c(Ai, A2,...) denotes a constant depending on the param-

eters Ai, A2,.... Such constants may be supposed to be effective, unless

it is pointed out explicitly that they are not;

o a statement S(x) is true for almost all x G N if the statement holds for

N + o(N) values of x iV, N — » 00. Similarly, a statement S(p) is true for

almost all p G P if it holds for

TT(7V)

+ o(ir(N)) values of p N, N - 00;

o the symbol • denotes the end of a proof.