function u = lorenzeqs(t,x)
global sigma r b

u = [sigma*(x(2)-x(1)), x(1)*(r - x(3)) - x(2), x(1)*x(2) - b*x(3)]';

% "Complex and Chaotic Nonlinear Dynamics. 
% Advances in Economics and Finance, 
% Mathematics and Statistics" 
% T.Vialar, Springer 2009.
% Copyright(c).