Search parameter for a reference example

{
  "resourceType" : "SearchParameter",
  "id" : "example-reference",
  "text" : {
    "status" : "extensions",
    "div" : "<div xmlns=\"http://www.w3.org/1999/xhtml\"><p><b>Generated Narrative: SearchParameter</b><a name=\"example-reference\"> </a></p><div style=\"display: inline-block; background-color: #d9e0e7; padding: 6px; margin: 4px; border: 1px solid #8da1b4; border-radius: 5px; line-height: 60%\"><p style=\"margin-bottom: 0px\">Resource SearchParameter &quot;example-reference&quot; </p></div><p><b>StructureDefinition Work Group</b>: fhir</p><p><b>url</b>: <code>http://hl7.org/fhir/SearchParameter/example-reference</code></p><p><b>name</b>: ExampleSearchParameter</p><p><b>title</b>: Example Search Parameter</p><p><b>status</b>: draft</p><p><b>experimental</b>: true</p><p><b>date</b>: 2013-10-23</p><p><b>publisher</b>: HL7 International / FHIR Infrastructure</p><p><b>contact</b>: [string]: <a href=\"http://www.hl7.org/Special/committees/fiwg\">http://www.hl7.org/Special/committees/fiwg</a></p><p><b>description</b>: Search by condition subject</p><p><b>purpose</b>: Need to search Condition by subject</p><p><b>code</b>: subject</p><p><b>base</b>: Condition</p><p><b>type</b>: reference</p><p><b>expression</b>: Condition.subject</p><p><b>processingMode</b>: normal</p><p><b>target</b>: Organization</p><p><b>modifier</b>: missing</p><p><b>chain</b>: name, identifier</p></div>"
  },
  "extension" : [{
    "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
    "valueCode" : "fhir"
  }],
  "url" : "http://hl7.org/fhir/SearchParameter/example-reference",
  "name" : "ExampleSearchParameter",
  "title" : "Example Search Parameter",
  "status" : "draft",
  "experimental" : true,
  "date" : "2013-10-23",
  "publisher" : "HL7 International / FHIR Infrastructure",
  "contact" : [{
    "name" : "[string]",
    "telecom" : [{
      "system" : "url",
      "value" : "http://www.hl7.org/Special/committees/fiwg"
    }]
  }],
  "description" : "Search by condition subject",
  "purpose" : "Need to search Condition by subject",
  "code" : "subject",
  "base" : ["Condition"],
  "type" : "reference",
  "expression" : "Condition.subject",
  "processingMode" : "normal",
  "target" : ["Organization"],
  "modifier" : ["missing"],
  "chain" : ["name",
  "identifier"]
}