In Lenore Thomson's theory, the four-letter code "INFJ" stands for a person with:

Introverted Intuition as their Dominant Function
Extraverted Feeling as their Secondary Function
Introverted Thinking as their Tertiary Function
Extraverted Sensation as their Inferior Function

Profiles

Bearing in mind the Classification Mismatches, here are:

Joe Butt's INFJ profile
David Keirsey's INFJ profile
Brenda Muller's INFJ profile
Hirsch and Kummerow's INFJ profile
Hale's INFJ profile

Here is an entire web site by, for, and about INFJs.

The Secondary Function for INFJs

Hypothesis: INFJs typically use their Secondary Function, Extraverted Feeling, to criticize the ways in which people are benefiting each other as being one-sided or to deflate people's attempts to gain respect and admiration in their society by contributing to it. "Snicker, snicker, this fellow's trying to look all altruistic, but notice how he makes sure that other people notice every time he does anything kind? C'mon, this is so transparently self-interested."

Development of the Secondary Function to gain a genuinely Extraverted balance might come by finding ways to benefit from other people. Fe as a channel for establishing and pursuing stakes in the extraverted world consists of creating mutual loyalty between yourself and others, so that you benefit as well as them. What do the people around you have to offer you? How can you show that you recognize that your fate is bound up with theirs--and collect your chips for making your contribution?