How do I work with Mongodb Queries in a node JS MEAN stack

I am using the linnovate MEAN boilerplate to build an application: https://github.com/linnovate/mean

With MongoDB I understand how to query a collection on the database and get the results via the command line such as:

db.articles.find({ 'title' : 'hello world'})

In the MEAN app the area I noticed for this type of querying is in the app/controllers/articles.js file:

/**
* List of Articles
*/
exports.all = function(req, res) {
    Article.find().sort('-created').populate('user', 'name username').exec(function(err, articles) {
        if (err) {
            res.render('error', {
                status: 500
            });
        } else {
            res.jsonp(articles);
        }
    });
};

If I wanted to add a way of returning another list with a specific query how would I go about that?Here is the code I'm working on:

exports.all = function(req, res) {
    Article.find().sort('-created').populate('user', 'name username').exec(function(err, articles) {
        if (err) {
            res.render('error', {
                status: 500
            });
        } else {
            res.jsonp(articles);
        Article.find({ 'category' : 'hello world').sort('-created').populate('user', 'name username').exec(function(err, morearticles) {
            if (err) {
                res.render('error', {
                    status: 500
                });
            } else {
                res.jsonp(morearticles);
            }
        });
        }
    });
};