diff --git a/datasetxml2oai-pmh.xslt b/datasetxml2oai-pmh.xslt
index 42f305d..b7b7b28 100755
--- a/datasetxml2oai-pmh.xslt
+++ b/datasetxml2oai-pmh.xslt
@@ -360,7 +360,7 @@
     
     <xsl:template match="SetSpec">
         <setSpec>
-            <xsl:value-of select="@Value" />
+            <xsl:value-of select="{Value}" />
         </setSpec>
     </xsl:template>
     
@@ -406,7 +406,7 @@
                 <xsl:text>doc-type:ResearchData</xsl:text>
             </dc:type>
             <!-- dc:format -->
-            <xsl:apply-templates select="File/@MimeType" mode="oai_dc" />
+            <xsl:apply-templates select="{File/MimeType}" mode="oai_dc" />
             <!-- <dc:format> -->
             <xsl:apply-templates select="File" mode="oai_dc" />
             <!-- dc:identifier -->
diff --git a/src/controllers/oai.controller.ts b/src/controllers/oai.controller.ts
index 76e936e..673d295 100644
--- a/src/controllers/oai.controller.ts
+++ b/src/controllers/oai.controller.ts
@@ -12,7 +12,7 @@ import { Dataset, Project, License } from "../models/init-models";
 import Logger from "jet-logger";
 import { BadOaiModelException, OaiModelException } from "../exceptions/OaiModelException";
 import PageNotFoundException from "../exceptions/PageNotFoundException";
-import { OaiErrorCodes } from "../exceptions/OaiErrorCodes";
+import { OaiErrorCodes, OaiModelError } from "../exceptions/OaiErrorCodes";
 import XmlModel from "../library/XmlModel";
 import Configuration from "../library/oai/OaiConfiguration";
 import ResumptionToken from "../library/oai/ResumptionToken";
@@ -89,7 +89,12 @@ export class OaiController {
             await this.handleRequest(oaiRequest, request);
         } catch (error) {
             if (error instanceof OaiModelException) {
-                this.xsltParameter["oai_error_code"] = error.oaiCode;
+                let code = error.oaiCode;
+                let oaiErrorCode: string | undefined = "Unknown oai error code " + code;
+                if (OaiModelError.has(error.oaiCode) && OaiModelError.get(code) != undefined) {
+                    oaiErrorCode = OaiModelError.get(error.oaiCode);
+                }
+                this.xsltParameter["oai_error_code"] = oaiErrorCode;
                 this.xsltParameter["oai_error_message"] = error.message;
             } else {
                 // return next(error); // passing to default express middleware error handler
@@ -255,6 +260,13 @@ export class OaiController {
             throw new BadOaiModelException("The prefix of the identifier argument is unknown.");
         }
         const dataId = Number(this.getDocumentIdByIdentifier(oaiRequest.identifier));
+        if (isNaN(dataId)) {
+            throw new OaiModelException(
+                StatusCodes.INTERNAL_SERVER_ERROR,
+                "The value of the identifier argument is illegal in this repository.",
+                OaiErrorCodes.BADARGUMENT,
+            );
+        }
 
         // let dataset: Dataset | null;
 
@@ -438,6 +450,14 @@ export class OaiController {
                 let fromDate = dayjs(from);
                 const until = oaiRequest["until"] as string;
                 let untilDate = dayjs(until);
+                if (!fromDate.isValid() || !untilDate.isValid()) {
+                    throw new OaiModelException(
+                        StatusCodes.INTERNAL_SERVER_ERROR,
+                        "Date Parameter is not valid.",
+                        OaiErrorCodes.BADARGUMENT,
+                    );
+                }
+
                 if (from.length != until.length) {
                     throw new OaiModelException(
                         StatusCodes.INTERNAL_SERVER_ERROR,
@@ -460,6 +480,13 @@ export class OaiController {
             } else if ("from" in oaiRequest && !("until" in oaiRequest)) {
                 const from = oaiRequest["from"] as string;
                 let fromDate = dayjs(from);
+                if (!fromDate.isValid()) {
+                    throw new OaiModelException(
+                        StatusCodes.INTERNAL_SERVER_ERROR,
+                        "From date parameter is not valid.",
+                        OaiErrorCodes.BADARGUMENT,
+                    );
+                }
                 fromDate.hour() == 0 && (fromDate = fromDate.startOf("day"));
 
                 const now = dayjs();
@@ -480,6 +507,13 @@ export class OaiController {
             } else if (!("from" in oaiRequest) && "until" in oaiRequest) {
                 const until = oaiRequest["until"] as string;
                 let untilDate = dayjs(until);
+                if (!untilDate.isValid()) {
+                    throw new OaiModelException(
+                        StatusCodes.INTERNAL_SERVER_ERROR,
+                        "Until date parameter is not valid.",
+                        OaiErrorCodes.BADARGUMENT,
+                    );
+                }
                 untilDate.hour() == 0 && (untilDate = untilDate.endOf("day"));
 
                 const firstPublishedDataset: Dataset = (await Dataset.earliestPublicationDate()) as Dataset;
diff --git a/src/exceptions/OaiErrorCodes.ts b/src/exceptions/OaiErrorCodes.ts
index 9842566..3cb2fd4 100644
--- a/src/exceptions/OaiErrorCodes.ts
+++ b/src/exceptions/OaiErrorCodes.ts
@@ -9,3 +9,42 @@ export enum OaiErrorCodes {
 
 // 👇️ default export
 // export { OaiErrorCodes };
+
+// https://medium.com/@juliapassynkova/map-your-typescript-enums-e402d406b229
+export const OaiModelError = new Map<number, string>([
+    [OaiErrorCodes.BADARGUMENT, 'badVerb'],
+    [OaiErrorCodes.BADARGUMENT, 'badArgument'],
+    [OaiErrorCodes.NORECORDSMATCH, 'noRecordsMatch'],
+    [OaiErrorCodes.CANNOTDISSEMINATEFORMAT, 'cannotDisseminateFormat'],
+    [OaiErrorCodes.BADRESUMPTIONTOKEN, 'badResumptionToken'],
+    [OaiErrorCodes.IDDOESNOTEXIST, 'idDoesNotExist']
+  ]);
+
+// class OaiModelError {
+//     // const BADVERB = 1010;
+//     // const BADARGUMENT = 1011;
+//     // const CANNOTDISSEMINATEFORMAT = 1012;
+//     // const BADRESUMPTIONTOKEN = 1013;
+//     // const NORECORDSMATCH = 1014;
+//     // const IDDOESNOTEXIST = 1015;
+   
+
+//     protected static $oaiErrorCodes = {
+//         OaiErrorCodes. 'badVerb',
+//         BADARGUMENT : 'badArgument',
+//         NORECORDSMATCH: 'noRecordsMatch',
+//         CANNOTDISSEMINATEFORMAT: 'cannotDisseminateFormat',
+//        BADRESUMPTIONTOKEN: 'badResumptionToken',
+//        IDDOESNOTEXIST: 'idDoesNotExist',
+//     };
+
+  
+    // public static function mapCode($code)
+    // {
+    //     if (false === array_key_exists($code, self::$oaiErrorCodes)) {
+    //         throw new OaiModelException("Unknown oai error code $code");
+    //     }
+    //     return self::$oaiErrorCodes[$code];
+    // }
+
+// }