Get entries relatedTo multiple categories I have searched and tried a few different ways but none have worked so not sure what is wrong.

Example say I have a few categories case studies, featured, articles, videos...

I have tried this way

{% set category = craft.categories.group('resource').relatedTo(
    'and',
    { targetElement: featured },
    { targetElement: case studies }
) %}
{% set entries = craft.entries.relatedTo(category).limit(3).find() %}


I have tried this way

{% set category = craft.categories({
    group: 'resource',
    relatedTo: [
        'and',
        { targetElement: featured },
        { targetElement: case-studies }
    ]
}) %}
{% set entries = craft.entries.relatedTo(category).limit(3).find() %}


I am wanting to find entries that use two categories together example case studies, and featured category.
The relatedTo parameter's targetElement property has to be an ElementCriteriaModel or a single category model:

{% set featured = craft.categories.group('myCatGroup').slug('featured').first() %}
{% set caseStudies = craft.categories.group('myCatGroup').slug('case-studies') %}

{% set entries = craft.users({
    group: 'resource',
    relatedTo: [
        'and',
        { targetElement: featured },
        { targetElement: caseStudies }
    ]
}) %}