Normalized intensity profiles of selected species towards L1489-IRS, B5-IRS1, L1455-IRS1, and L1551-IRS5. The profiles of SO, c-C₃H₂, H₂CO (in all sources), CH₃OH, CH₃CHO, HCOOCH₃ (in L1551-IRS5), and OCS (in L1455-IRS1) were obtained by stacking the detected transitions for each species in order to maximize the S/N. CH₃OH (4_−2,3 –3_−1,2E) in B5-IRS1 and L1455-IRS1 is the transition at 218 440 MHz; H₂CS (7_1,7 –6_1,6) in B5-IRS1, L1455-IRS1, and L1551-IRS5 is the transition at 236 727 MHz; H₂S (2_2,0 –2_1,1) in L1455-IRS1 and L1551-IRS5 is the transition at 216 710 MHz; OCS (19–18) in L1551-IRS5 is the transition in 231 060 MHz.