Latex - Multiple references in one citation

minger

Guys,

I am trying to get my citations to do a "through" type thing, ala,. . .gotten using this method [1-4].

Rather, I am getting an entire listing, ala. . . gotten using this method [1, 2, 3, 4].

I am simply using
which from what I understand should be enough. Is there an issue with my bibstyle?

I am using the elsarticle class and elsarticle-num.bst if anyone is familiar with them. I have access to the other .bst classes if anyone can recommend one to remedy this situation.