Specific angular momentum as a function of core radius measured with different lines. Large symbols show protostellar cores, small symbols show starless cores. The lines are the best fits of a power-law function aR^b calculated for each species (N₂H⁺(1–0) – blue, N₂D⁺(2–1) – red, H¹³CO⁺(1–0) – green, DCO⁺(2–1) – yellow), a and b values are given in the main text. The black line shows the relation found by Goodman et al. (1993). Thick light colour strips represent the accuracies of the fits (N₂H⁺(1–0) – light blue, N₂D⁺(2–1) – light red, H¹³CO⁺(1–0) – light green, DCO⁺(2–1) – light yellow, Goodman et al. 1993 – grey).