ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C4H2O4/c5-1-2(6)4(8)3(1)7/h5-6H/file?format=sdf&get3d=True  -- InChI=1S/C4H2O4/c5-1-2(6)4(8)3(1)7/h5-6H could not be loaded.