Joint confidence contours on the i-Ω-grid for HD 140667 (left), HD 158222 (centre), HD 217924 (right). The contour lines correspond to confidences at 1-σ (solid), 2-σ (dashed), 3-σ (dotted), and 4-σ (dash-dotted) level. The crosses indicate the position of the best non-linear adjustment solution for each of the 100 Monte Carlo samples of spectroscopic parameters and the star corresponds to the adopted orbit.