Thread: static declaration creates linker error

When I run the code below with the private LinkedList declared without the static qualifier, it compiles and runs exactly as I expect. As soon as I add the static declaration, I get linker errors and it can't find the LinkedList. Any thoughts?

Code:

#ifndef CS240_URL_SET_H
#define CS240_URL_SET_H

//Dustin Nicholes
//October 21, 2008
//CS 240
//URLSet.h

#include "URL.h"
#include "LinkedList.h"
#include "StringUtil.h"

class URLSet
{
	private:
		static LinkedList<URL> urlSet;
	public:
		URLSet()
		{}
	
		bool addURL(URL & url)
		{
			if(!Contains(url))
			{
				urlSet.Insert(new URL(url), NULL);
				return true;
			}
			return false;
		}
		
		bool Contains(URL & url)
		{
			LLNode<URL> *LLCurrent;
			LLCurrent=urlSet.GetFirst();
			string scheme = StringUtil::ToLowerCopy(url.getScheme());
			string netLoc = StringUtil::ToLowerCopy(url.getNetLocation());
			string path = url.getPath();
			
			while(LLCurrent)
			{
				string otherString((LLCurrent->value)->toString());
				URL other(otherString);
				string otherScheme = StringUtil::ToLowerCopy(other.getScheme());
				string otherNetLoc = StringUtil::ToLowerCopy(other.getNetLocation());
				string otherPath = other.getPath();
				
				string thisString(scheme+netLoc+path);
				string thatString(otherScheme+otherNetLoc+otherPath);
				
				if(thisString.compare(thatString)==0)
					return true;
				LLCurrent = LLCurrent->next;
			}
			return false;
		}
		
		static bool Test(ostream & os)
		{
			os<<"Starting URL Set Test: ";
			bool success = true;
			
			string urlString("http://students.cs.byu.edu/~cs240ta/util_docs/");
			URL url1(urlString);
			urlString="http://students.cs.byu.edu/~cs240ta/fall2008/";
			URL url2(urlString);
			urlString="http://students.cs.byu.edu/~cs240ta/fall2008/TA/";
			URL url3(urlString);
			urlString="HtTp://students.cs.byu.edu/~cs240ta/fall2008/TA/";
			URL url4(urlString);
			urlString="http://students.cs.byu.edu/bogus/";
			URL url5(urlString);
			
			URLSet testSet;
			TEST(testSet.addURL(url1));
			TEST(testSet.addURL(url2));
			TEST(testSet.addURL(url3));
			TEST(!testSet.addURL(url4));
			
			TEST(testSet.Contains(url1));
			TEST(testSet.Contains(url2));
			TEST(testSet.Contains(url3));
			TEST(!testSet.Contains(url5));
						
			if(success)
				os<<"Passed\r\n";
			else
				os<<"Failed!!\r\b";
			
			return success;
		}
};

#endif