url - multiple languages in htaccess rewriterule

Question

This rewrite rule in my htaccess works fine:

Options +FollowSymLinks
RewriteEngine On 
RewriteBase / 

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

RewriteRule ^(.+?/)?([^/]+).html$ /$1content.php?page=$2&lang=en [L] 
RewriteCond %{THE_REQUEST} ^(GET|HEAD)\ (/.*?)?/content.php\?page=([^&\ ]+) 
RewriteRule ^(.+?/)?content.php$ /$2%3.html? [L,R=301]

Question: I like to use another language. In the end of the first RewriteRule it says.... &lang=en What do I need to do to make also e.g. a dutch language work? &lang=nl ?