The notion of the family boundary curves (FBC), introduced recently fo
r two-dimensional conservative systems, is extended to account for, ge
nerally, nonconservative autonomous systems of two degrees of freedom.
Formulae are found for the force components X(x, y), Y(x, y) which pr
oduce a preassigned family of orbits f(x, y) = c lying inside a preass
igned, open or closed, region B(x, y) greater-than-or-equal-to 0 of th
e xy plane.