what is the {statement is subject of} for {Nigeria} has {diplomatic relation} as {Cameroon} ?
What agreements are in place to regulate the diplomatic relation between Nigeria and Cameroon?
What is the statement is subject of Nigeria whose diplomatic relation is Cameroon?
SELECT ?l WHERE { ?d property:statement_is_subject_of ?l . resource:Nigeria property:diplomatic_relation ?d . ?d property:diplomatic_relation resource:Cameroon }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q1033> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P530> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q1009> .
?statement <http://www.wikidata.org/entity/P805> ?value. 
} 

SELECT ?value WHERE { wd:Q1033 p:P530 ?s . ?s ps:P530 wd:Q1009 . ?s pq:P805 ?value}