laravel-snappy css files

How to include external css files with laravel to make it work ? It's not converting because of error. When i try to convert simple html without including any css files - it works perfect. I tried both url() and asset() helpers. Also i tried absolute path like: {{ public_path('css/app.css') }} and it's not only didn't generate pdf, but also css files was not load on the page and all my styling disappears. Here my view:

    @extends('layouts.app')

@section('title')
    TEST
@endsection

@section('content')
<div class="container">
    <div class="row">
        <div class="col-md-12 welcome-screen">
            <h1 class="TEST-welcome-logo"><img src="{{ url('/img/home-logo.jpg') }}"></h1>
        </div>
    </div>
</div>
@endsection

It's layouts/app.php:

<!-- Styles -->
    <link href="{{ url('bootstrap/css/bootstrap.min.css') }}" rel="stylesheet">
    <link href="{{ url('css/datatables.min.css') }}" rel="stylesheet">
    <link href="{{ url('css/selectize.bootstrap3.css') }}" rel="stylesheet">
    <link href="{{ url('css/jquery-ui.min.css') }}" rel="stylesheet">
    <link href="{{ url('css/bootstrap-datetimepicker.min.css') }}" rel="stylesheet">
    <link rel="stylesheet" type="text/css" href="{{ url('css/sweetalert.css') }}">
    <link href="{{ url('css/app.css') }}" rel="stylesheet">

Here's output error in laravel.log file:

[2017-03-22 15:18:19] local.ERROR: RuntimeException: The exit status code '1' says something went wrong:
stderr: "Loading pages (1/6)
[>                                                           ] 0%
[======>                                                     ] 10%
[=======>                                                    ] 12%
Warning: Failed to load file:///uploads/7abde879392e5298903cb5946ba58aef271e28c158e7140ce183ed34574a9c44.jpg (ignore)
Warning: Failed to load http://localhost/css/sweetalert.css (ignore)
Warning: Failed to load http://localhost/css/app.css (ignore)
Warning: Failed to load http://localhost/js/moment.js (ignore)
Warning: Failed to load http://localhost/js/bootstrap-wysiwyg.js (ignore)
Warning: Failed to load http://localhost/js/app.js (ignore)
Warning: Failed to load http://localhost/img/info-book.png (ignore)
Warning: Failed to load http://localhost/img/home-logo.jpg (ignore)
Warning: Failed to load http://localhost/img/ditaso-footer.png (ignore)
[=======>                                                    ] 13%
[============================================================] 100%
Counting pages (2/6)                                               
[============================================================] Object 1 of 1
Resolving links (4/6)                                                       
[============================================================] Object 1 of 1
Loading headers and footers (5/6)                                           
Printing pages (6/6)
[>                                                           ] Preparing
[==============================>                             ] Page 1 of 2
[============================================================] Page 2 of 2
Done                                                                      
Exit with code 1 due to network error: ConnectionRefusedError
"
stdout: ""
command: /var/www/laravel/vendor/h4cc/wkhtmltopdf-amd64/bin/wkhtmltopdf-amd64 --lowquality --print-media-type --viewport-size '1024x1500' '/tmp/knp_snappy58d295bb4634b4.16726344.html' '/tmp/knp_snappy58d295bb463d41.83569796.pdf'. in /var/www/laravel/vendor/knplabs/knp-snappy/src/Knp/Snappy/AbstractGenerator.php:336