fast frenglish mode:
you can find the lightwave binary description format (.lwo) with each lightwave installation, on amiga or PC. (there are 2 generations of lwo, LWOB that has no texture mapping coordinates per vertex, and LWO2 that has this feature (also, it does uncontinuous mapping since LW6.5 if you understand).) I guess you can always get the LWO2 description from the newtek lightwave site, in the dev. pac.
http://www.newtek.com/lightwave/developer/LW80/8lw sdk/docs/filefmts/lwo2.html
note lightwave use .lwo only for object descrition, scenes are described on text file based ".lws"
the .3DS format is from the oooold PC-DOS 3DS Studio (3/4) , (which was made by Dan silva , autor of deluxe paint, by the way). ".3ds" files handles texture coordinates per vertex, but not discontinuous mapping. the .3ds format was explained and became public when the first "3DS MAX" was out.
the current new 3dmax files is a closed format, but you have the source code of a ".3ds" exporter with each 3dsmax. Also, a single .3ds contains many objects and scene descriptions.
and to finish, lib3ds is a gpl lib used by a lots of demoscene groups, that just read a ".3ds" file and describe it, so that you just use the 3ds exporter on max. (One of the best ASD demo was coded in 2 month using it, i read.)
http://sourceforge.net/projects/lib3ds/