Hi Myrian,
To find all entities related to the Matthew Effect in Wikidata - you have 2 options:
1) Go to the entity in your browser: https://www.wikidata.org/wiki/Q1337985
Or 2) Send a SPARQL query to Wikidata's SPARQL endpoint: https://query.wikidata.org/
The Matthew Effect has the Wikidata entity ID Q1337985, so you can send a query like this one:
SELECT ?p ?o
WHERE {
wd:Q1337985 ?p ?o .
}
This will return all triples that contain the Matthew Effect as the subject. You can reverse this to find all the triples in which it is the object.
Thanks for reading and enjoy!