fix issue #2

README.adoc

@@ -55,21 +55,21 @@ end
 
 === Retrieving bibliographic items using OpenLibrary API
 
-To retrieve bibliographic items, use `RelatonIsbn::OpenLibrary.get` method with ISBN-10 or ISBN-13 as an argument. Prefix `ISBN` and hyphens are optional. The method returns `RelatonBib::BibliographicItem` object.
+To retrieve bibliographic items, use `RelatonIsbn::OpenLibrary.get` method with ISBN-10 or ISBN-13 as an argument. Allowed prefixes are `ISBN`, `isbn:`. Prefix and hyphens are optional. The method returns `RelatonBib::BibliographicItem` object.
 
 [source,ruby]
 ----
 # get document by ISBN-13
-> bibitem = RelatonIsbn::OpenLibrary.get "ISBN 978-0-12-064481-0"
+> ibitem = RelatonIsbn::OpenLibrary.get "ISBN 978-0-12-064481-0"
 [relaton-isbn] (ISBN 9780120644810) Fetching from OpenLibrary ...
 [relaton-isbn] (ISBN 9780120644810) Found: `9780120644810`
 => #<RelatonBib::BibliographicItem:0x0000000113889258
 ...
 
 # get document by ISBN-10
-> RelatonIsbn::OpenLibrary.get "0120644819"
-[relaton-isbn] (ISBN 0120644819) Fetching from OpenLibrary ...
-[relaton-isbn] (ISBN 0120644819) Found: `9780120644810`
+> RelatonIsbn::OpenLibrary.get "isbn:0120644819"
+[relaton-isbn] (isbn:0120644819) Fetching from OpenLibrary ...
+[relaton-isbn] (isbn:0120644819) Found: `9780120644810`
 => #<RelatonBib::BibliographicItem:0x00000001098ac960
 ...
 ----

lib/relaton_isbn/isbn.rb

@@ -6,7 +6,7 @@ class Isbn
     # @param [String] isbn ISBN 13 number
     #
     def initialize(isbn)
-      @isbn = isbn&.delete("-")&.sub(/^ISBN\s/, "")
+      @isbn = isbn&.delete("-")&.sub(/^ISBN[\s:]/i, "")
     end
 
     def parse

lib/relaton_isbn/version.rb

@@ -1,3 +1,3 @@
 module RelatonIsbn
-  VERSION = "1.18.0".freeze
+  VERSION = "1.18.1".freeze
 end

spec/relaton_isbn/isbn_spec.rb

@@ -29,6 +29,16 @@
     it "with nil" do
       expect(described_class.new(nil).parse).to be_nil
     end
+
+    context "with prefix" do
+      it "ISBN" do
+        expect(described_class.new("ISBN 0-12-064481-9").parse).to eq "9780120644810"
+      end
+
+      it "isbn:" do
+        expect(described_class.new("isbn:0-12-064481-9").parse).to eq "9780120644810"
+      end
+    end
   end
 
   context "check ISBN" do