<Router>
        <div className="app">
            <GlobalContextProvider>
                <Header />
                <Switch>
                    <Route path="/CodeSystem" component={PageCodeSystem} />
                    <Route path="/ValueSet" component={PageValueSet} />
                    <Route path="/RefSets" component={PageRefSets} />
                    <Route path="/" exact component={HomePage} />
                </Switch>
            </GlobalContextProvider>
        </div>
    </Router>