Data citation information is stored in Event Data. See the Event Data API guide for more information about how to consume information about data citation.

Let's look at a simple example. To consume DOI citations we need to call the events endpoint and filter by the Crossref source and the prefix.

curl  "https://api.test.datacite.org/events?mailto=YOUR_EMAIL_HERE&source-id=crossref&prefix=10.5438"

You will retrieve a JSONAPI response. The JSONAPI responses have three main objects: data, links and meta. We will focus on the data object, as this object contains all the information we want. There are a few important things to consider. First, the attribute data is an array and contains the metadata for all the usage metrics for the prefix found by the query.

"data":[
      {
         "id":"4bcd1887-da05-448b-87b2-65952fb2196e",
         "type":"events",
         "attributes":{
            "subj-id":"https://doi.org/10.1007/s11082-018-1327-1",
            "obj-id":"https://doi.org/10.5438/0012",
            "source-id":"crossref",
            "relation-type-id":"references",
            "total":1,
            "message-action":"create",
            "source-token":"8676e950-8ac5-4074-8ac3-c0a18ada7e99",
            "license":"https://doi.org/10.13003/CED-terms-of-use",
            "occurred-at":"2018-01-17T00:00:00.000Z",
            "timestamp":"2018-12-12T08:36:09.475Z"
         },
         "relationships":{
            "subj":{
               "data":{
                  "id":"https://doi.org/10.1007/s11082-018-1327-1",
                  "type":"objects"
               }
            },
            "obj":{
               "data":{
                  "id":"https://doi.org/10.5438/0012",
                  "type":"objects"
               }
            }
         }
      },
      {
         "id":"d3367112-4c66-4811-9c66-b023ba68565f",
         "type":"events",
         "attributes":{
            "subj-id":"https://doi.org/10.4018/978-1-5225-2221-8.ch003",
            "obj-id":"https://doi.org/10.5438/0005",
            "source-id":"crossref",
            "relation-type-id":"references",
            "total":1,
            "message-action":"create",
            "source-token":"8676e950-8ac5-4074-8ac3-c0a18ada7e99",
            "license":"https://doi.org/10.13003/CED-terms-of-use",
            "occurred-at":"0000-01-01T00:00:00.000Z",
            "timestamp":"2018-12-12T08:43:00.513Z"
         },
         "relationships":{
            "subj":{
               "data":{
                  "id":"https://doi.org/10.4018/978-1-5225-2221-8.ch003",
                  "type":"objects"
               }
            },
            "obj":{
               "data":{
                  "id":"https://doi.org/10.5438/0005",
                  "type":"objects"
               }
            }
         }
      },
      {
         "id":"c318acc2-5056-4f94-a007-0ec890f7c49e",
         "type":"events",
         "attributes":{
            "subj-id":"https://doi.org/10.4018/978-1-5225-0700-0.ch001",
            "obj-id":"https://doi.org/10.5438/0010",
            "source-id":"crossref",
            "relation-type-id":"references",
            "total":1,
            "message-action":"create",
            "source-token":"8676e950-8ac5-4074-8ac3-c0a18ada7e99",
            "license":"https://doi.org/10.13003/CED-terms-of-use",
            "occurred-at":"0000-01-01T00:00:00.000Z",
            "timestamp":"2018-12-12T08:43:50.172Z"
         },
         "relationships":{
            "subj":{
               "data":{
                  "id":"https://doi.org/10.4018/978-1-5225-0700-0.ch001",
                  "type":"objects"
               }
            },
            "obj":{
               "data":{
                  "id":"https://doi.org/10.5438/0010",
                  "type":"objects"
               }
            }
         }
      },
      {
         "id":"aef8403b-6f14-408b-8615-e542533107cb",
         "type":"events",
         "attributes":{
            "subj-id":"https://doi.org/10.1007/978-3-319-67008-9_7",
            "obj-id":"https://doi.org/10.5438/0012",
            "source-id":"crossref",
            "relation-type-id":"references",
            "total":1,
            "message-action":"create",
            "source-token":"8676e950-8ac5-4074-8ac3-c0a18ada7e99",
            "license":"https://doi.org/10.13003/CED-terms-of-use",
            "occurred-at":"2017-01-01T00:00:00.000Z",
            "timestamp":"2018-12-12T08:44:30.071Z"
         },
         "relationships":{
            "subj":{
               "data":{
                  "id":"https://doi.org/10.1007/978-3-319-67008-9_7",
                  "type":"objects"
               }
            },
            "obj":{
               "data":{
                  "id":"https://doi.org/10.5438/0012",
                  "type":"objects"
               }
            }
         }
      },
      {
         "id":"ce40fee4-3818-4f9e-8833-734211d2d9e2",
         "type":"events",
         "attributes":{
            "subj-id":"https://doi.org/10.1080/19386389.2018.1439278",
            "obj-id":"https://doi.org/10.5438/0015",
            "source-id":"crossref",
            "relation-type-id":"references",
            "total":1,
            "message-action":"create",
            "source-token":"8676e950-8ac5-4074-8ac3-c0a18ada7e99",
            "license":"https://doi.org/10.13003/CED-terms-of-use",
            "occurred-at":"2017-10-02T00:00:00.000Z",
            "timestamp":"2018-12-12T08:54:46.962Z"
         },
         "relationships":{
            "subj":{
               "data":{
                  "id":"https://doi.org/10.1080/19386389.2018.1439278",
                  "type":"objects"
               }
            },
            "obj":{
               "data":{
                  "id":"https://doi.org/10.5438/0015",
                  "type":"objects"
               }
            }
         }
      },
      {
         "id":"919bcfa0-5049-4593-a56e-511feb860564",
         "type":"events",
         "attributes":{
            "subj-id":"https://doi.org/10.1007/978-3-658-16937-4_4-1",
            "obj-id":"https://doi.org/10.5438/0012",
            "source-id":"crossref",
            "relation-type-id":"references",
            "total":1,
            "message-action":"create",
            "source-token":"8676e950-8ac5-4074-8ac3-c0a18ada7e99",
            "license":"https://doi.org/10.13003/CED-terms-of-use",
            "occurred-at":"2018-01-01T00:00:00.000Z",
            "timestamp":"2018-12-12T09:04:20.976Z"
         },
         "relationships":{
            "subj":{
               "data":{
                  "id":"https://doi.org/10.1007/978-3-658-16937-4_4-1",
                  "type":"objects"
               }
            },
            "obj":{
               "data":{
                  "id":"https://doi.org/10.5438/0012",
                  "type":"objects"
               }
            }
         }
      },
      {
         "id":"2f056f6e-96e4-469d-ac0b-5f18ec4be531",
         "type":"events",
         "attributes":{
            "subj-id":"https://doi.org/10.4018/978-1-5225-6921-3.ch019",
            "obj-id":"https://doi.org/10.5438/0005",
            "source-id":"crossref",
            "relation-type-id":"references",
            "total":1,
            "message-action":"create",
            "source-token":"8676e950-8ac5-4074-8ac3-c0a18ada7e99",
            "license":"https://doi.org/10.13003/CED-terms-of-use",
            "occurred-at":"0000-01-01T00:00:00.000Z",
            "timestamp":"2018-12-12T09:04:46.481Z"
         },
         "relationships":{
            "subj":{
               "data":{
                  "id":"https://doi.org/10.4018/978-1-5225-6921-3.ch019",
                  "type":"objects"
               }
            },
            "obj":{
               "data":{
                  "id":"https://doi.org/10.5438/0005",
                  "type":"objects"
               }
            }
         }
      }
   ],
   "meta":{
      "total":7,
      "total-pages":1,
      "page":1,
      "sources":[
         {
            "id":"crossref",
            "title":"Crossref to DataCite",
            "count":7
         }
      ],