@java.lang.Override
  public int getSerializedSize() {
    int size = memoizedSize;
    if (size != -1) return size;

    size = 0;
    if (startIndex_ != 0) {
      size += com.google.protobuf.CodedOutputStream.computeInt32Size(1, startIndex_);
    }
    if (endIndex_ != 0) {
      size += com.google.protobuf.CodedOutputStream.computeInt32Size(2, endIndex_);
    }
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(uri_)) {
      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(3, uri_);
    }
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(title_)) {
      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(4, title_);
    }
    if (!com.google.protobuf.GeneratedMessageV3.isStringEmpty(license_)) {
      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(5, license_);
    }
    if (((bitField0_ & 0x00000001) != 0)) {
      size += com.google.protobuf.CodedOutputStream.computeMessageSize(6, getPublicationDate());
    }
    size += getUnknownFields().getSerializedSize();
    memoizedSize = size;
    return size;
  }
<pre>
Output only. Publication date of the attribution.
</pre>

<code>.google.type.Date publication_date = 6 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/Citation.java