noticed a possible problem for the Volvo construction vehicles

some are listed with make Volvo BM while other like this just as Volvo
http://www.imcdb.org/vehicles.php?resultsStyle=asImages&yearFrom=&yearTo=&makeMatch=- 2&make=volvo&modelMatch=1&model=&modelInclModel=on&modelInclChassis=on&class106=- 106&origin=&madein=&madefor=&role=


how should it be correct then ?

It depends on the year... they were Volvo BM from 1973(?) until the late 90's? Then just Volvo afterward. I don't know the years. I'm sure you'll do some research on it

According to http://en.wikipedia.org/wiki/Volvo_BM it changed to Volvo Construction Equipment in 1995 (so just Volvo as make)
But as Owlman said, before that they were Volvo BM.

Volvo Construction Equipment modelyear history:

1832-1932 Munktells Mekaniska Verkstad
1844-1932 Bolinders
1932-1950 Bolinder-Munktell
1950-1971 BM Volvo
1972-1995 Volvo BM
1995 and on is Volvo (some vehicles carried the Volvo BM badge up until 1997)