diff --git a/src/library_client.ts b/src/library_client.ts
index c1baffb..204bdfd 100644
--- a/src/library_client.ts
+++ b/src/library_client.ts
@@ -1,3 +1,6 @@
+// https://gist.github.com/didiercrunch/8fbe1e26595e41817c92bed4efc44bcd
+import {Book} from "./library_server.ts"
+
 async function getPing(): Promise<void> {
     const resp = await fetch("http://localhost:3000/ping")
     const text = await resp.text()
@@ -12,8 +15,8 @@ function extractIsbn(rawResponse: any): string[]{
     return ret;
 }
 
-async function getAllIsbn(){
-    const resp = await fetch("http://localhost:3000/books")
+async function getAllIsbn(): Promise<string[]>{
+    const resp = await fetch("http://localhost:3000/books");
     const ret = await resp.json();
     return extractIsbn(ret);
 
@@ -42,9 +45,20 @@ async function createFourBooks(): Promise<void>{
     await createBook("3333", "jk rolling", "harry potter IV", 2007);
 }
 
-async function getCreateBook(): Promise<void> {
-    await createFourBooks();
-    console.log(await getAllIsbn());
+async function getBook(isbn: string): Promise<Book>{
+    const url = "http://localhost:3000/books/" + isbn;
+    const resp = await fetch(url);
+    const ret = await resp.json();
+    return ret;
+
 }
 
-await getCreateBook();
\ No newline at end of file
+async function petitTest(): Promise<void> {
+    await createFourBooks();
+    const isbns = await getAllIsbn();
+    for(const isbn of isbns){
+        console.log(await getBook(isbn));
+    }
+}
+
+await petitTest();
\ No newline at end of file
diff --git a/src/library.ts b/src/library_server.ts
similarity index 63%
rename from src/library.ts
rename to src/library_server.ts
index 8f06e69..a5524ec 100644
--- a/src/library.ts
+++ b/src/library_server.ts
@@ -1,3 +1,5 @@
+// https://gist.github.com/didiercrunch/f605ec5bdb034f3eb2acd3cf0b858895
+
 // @deno-types="npm:@types/express@4"
 import express, {Response, Request} from "npm:express@4";
 import bodyParser from "npm:body-parser@1.20.2";
@@ -7,14 +9,14 @@ const app = express()
 app.use(bodyParser.json());
 
 
-type Book = {
+export type Book = {
     isbn: string,
     author: string,
     title: string,
     publicationYear: number,
 }
 
-const library : Book[] = [];
+const library_server : Book[] = [];
 
 function bookAlreadyExists(book: Book, library: Book[]): boolean{
     for(const bookInLibrary of library){
@@ -33,13 +35,22 @@ function isValidBook(maybeBook: any){
         && "publicationYear" in maybeBook;
 }
 
+function getBookByIsbn(isbn: string, library: Book[]): Book | null {
+    for(const bookInLibrary of library){
+        if(bookInLibrary.isbn === isbn){
+            return bookInLibrary;
+        }
+    }
+    return null;
+}
+
 app.get("/ping", (req: Request, res: Response): void => {
     res.send("pongi");
 })
 
 app.get("/books", (req: Request, res: Response): void => {
     const books = [];
-    for(const book of library){
+    for(const book of library_server){
         books.push({isbn: book.isbn});
     }
     const ret = {
@@ -48,15 +59,26 @@ app.get("/books", (req: Request, res: Response): void => {
     res.send(ret);
 });
 
+app.get("/books/:isbn", (req: Request, res: Response): void => {
+    const isbn = req.params.isbn;
+    const book = getBookByIsbn(isbn, library_server);
+    if(book === null){
+        res.status(404);
+        res.send({});
+        return
+    }
+    res.send(book);
+});
+
 app.post("/books", (req: Request, res: Response): void => {
     const book = req.body;
-    if(!isValidBook(book) || bookAlreadyExists(book, library)){
+    if(!isValidBook(book) || bookAlreadyExists(book, library_server)){
         res.status(400);
         res.send({})
         return;
     }
 
-    library.push(book);
+    library_server.push(book);
     res.send(book);
 });