About: http://webisa.webdatacommons.org/204813154

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	I do not remember the source, but I am pretty sure it was said that Spike's ability to send letters is a spell he was taught by Celestia.
http://www.w3.org/ns/prov#wasQuotedFrom	tvtropes.org