c++ - Unresolved External symbol

I am getting a linking error, and I'm not sure what its referring to.

Here is the error

1>Main.obj : error LNK2019: unresolved external symbol "public: void __thiscall BinaryHeap,class std::allocator > >,class Comp,class std::allocator > > >::insert(class Item,class std::allocator > > const &)" (?insert@?$BinaryHeap@V?$Item@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@@V?$Comp@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@@@@QAEXABV?$Item@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@@@Z) referenced in function "public: void __thiscall PriorityQueue,class std::allocator > >::insertItem(int,class std::basic_string,class std::allocator > const &)" (?insertItem@?$PriorityQueue@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@@QAEXHABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z)

The code is rather long, however if you want me to post it I will.

thanks