stl find_if msvs6.0

#include "Order.h"
#include <list>
#include <iostream>
#include <algorithm>
#include "stdafx.h"
 
using namespace std;
 
namespace Search
{
list<Order>::iterator SearchPaid(list<Order> & orders);
list<Order>::iterator SearchNotPaid(list<Order> & orders);
list<Order>::iterator SearchNotPaid(list<Order> & orders, double border);
list<Order>::iterator SearchClient(list<Order> & orders, const char * client);
list<Order>::iterator SearchCost(list<Order> & orders, double cost);
 
 
}
 
/*.....*/
list<Order>::iterator Search::SearchPaid(list<Order> & orders)
{
    return find_if(orders.begin(), orders.end(), isPaid);
}
list<Order>::iterator Search::SearchNotPaid(list<Order> & orders)
{
    return find_if(orders.begin(), orders.end(), isNotPaid);
}
list<Order>::iterator Search::SearchNotPaid(list<Order> & orders, double border)
{
 
    return find_if(orders.begin(), orders.end(), PredBord(border));
}
list<Order>::iterator Search::SearchClient(list<Order> & orders,
        const char * client)
{
    sort(orders.begin(), orders.end(), ClientSort());
    return find_if(orders.begin(), orders.end(), ClientSearch(client));
}
list<Order>::iterator Search::SearchCost(list<Order> & orders, double cost)
{
    sort(orders.begin(), orders.end());
    return find_if(orders.begin(), orders.end(), CostSearch(cost));
}

search.cpp(99) : error C2065: 'find_if' : undeclared identifier
search.cpp(109) : error C2065: 'sort' : undeclared identifier

using namespace std;