"CODE" 35173;
    "PROCEDURE" BESS K01(X, K0, K1); "VALUE" X; "REAL" X, K0, K1;
    "IF" X <= 1.5 "THEN"
    "BEGIN" "INTEGER" K; "REAL" C, D, R, S, SUM0, SUM1, T,
        TERM, T0, T1;
        SUM0:= D:= LN(2/X) -.5772156649015328606;
        SUM1:=    C:= -1 -2    * D; R:= TERM:= 1; T:= X * X/4;
        "FOR" K:= 1,K+1 "WHILE" ABS(T0/SUM0) + ABS(T1/SUM1) >
        "-15 "DO"
        "BEGIN"  TERM:= T * TERM * R * R; D:= D + R;
            C:= C - R; R:= 1/(K+1); C:= C - R;
            T0:= TERM * D; T1:= TERM * C * R;
            SUM0:= SUM0 + T0; SUM1:= SUM1 + T1
        "END";
        K0:= SUM0; K1:= (1 + T * SUM1) / X
    "END" "ELSE"
    "BEGIN" "REAL" EXPX;
        EXPX:= EXP(- X);
        NONEXP BESS K01(X, K0, K1); K1:= EXPX * K1; K0:= K0 * EXPX
    "END" BESS K01;
        "EOP"