diff --git a/src/glxml.gleam b/src/glxml.gleam
index dbed3b1..7b270eb 100644
--- a/src/glxml.gleam
+++ b/src/glxml.gleam
@@ -6,15 +6,35 @@ import gleam/option.{type Option, None, Some}
 import gleam/result
 import gleam/string
 
+pub type Content {
+  Empty
+  Any
+  Mixed(content: List(String))
+  Choice(content: ContentParticle)
+}
+
 pub type Declaration {
   XMLDecl(versioninfo: String, encoding: String, standalone: Bool)
   GEntityDecl
   PEntityDecl(name: String, decl: String)
-  ElementDecl
+  ElementDecl(name: String, content: Content)
   AttListDecl
   NotationDecl
 }
 
+pub type Optional {
+  One
+  OneOrMore
+  ZeroOrMore
+  ZeroOrOne
+}
+
+pub type ContentParticle {
+  ElParticle(name: String, optional: Optional)
+  ChoiceParticle(choices: List(ContentParticle), optional: Optional)
+  SeqParticle(seq: List(ContentParticle), optional: Optional)
+}
+
 pub type Entity {
   InternalEntity(value: String)
   SystemExternalEntity(literal: String)
@@ -58,14 +78,15 @@ pub type Element {
 
 pub fn main() {
   parse_document(
+    "<?xml version=\"1.1\"?>\r\n<!DOCTYPE el [\r\n<!ELEMENT div1 (head, (p | list | note)*, div2*)>\r\n]>",
     //"<?xml version=\"1.1\" encoding='UTF-8'?>\r\n   <!-- hello-world -->   \n<b blah:test='1'><a attr='ha&#x20;&#38;#38;ha' battr='baba' ref='&amp;'/><!-- ma comment --><![CDATA[Testing&&<haha>]]><?test asuhashd ?></b>",
-    // "<doc>
-    "<doc>
-<A a=\"asdf>'&#34;>
-asdf
-	?>%\"/>
-<A a='\"\">&#39;&#34;'/>
-</doc>",
+  // "<doc>
+  //     "<doc>
+  // <A a=\"asdf>'&#34;>
+  // asdf
+  // 	?>%\"/>
+  // <A a='\"\">&#39;&#34;'/>
+  // </doc>",
   )
   |> echo
 }
@@ -284,7 +305,7 @@ fn parse_attribute(
   doc: String,
   doctype: Option(DocType),
 ) -> Result(#(Attribute, String), Nil) {
-  let doc = trim_space(doc)
+  use doc <- result.try(trim_mandatory_space(doc))
   use #(name, doc) <- result.try(parse_name(doc))
   case doc {
     "=" <> tail -> {
@@ -461,7 +482,7 @@ fn parse_prolog(
 fn parse_doctype(doc: String) -> Result(#(DocType, String), Nil) {
   case doc {
     "<!DOCTYPE" <> tail -> {
-      let doc = trim_space(tail)
+      use doc <- result.try(trim_mandatory_space(tail))
       use #(name, doc) <- result.try(parse_name(doc))
 
       let #(external_id, doc) =
@@ -518,11 +539,241 @@ fn do_parse_int_subset(
       }
     }
     _ -> {
-      todo
+      case
+        try_parsers(
+          [
+            parse_elementdecl,
+          ],
+          doc,
+        )
+      {
+        Ok(#(decl, doc)) -> {
+          do_parse_int_subset(doc, [decl, ..decl_list])
+        }
+        Error(_) -> Ok(#(list.reverse(decl_list), doc))
+      }
     }
   }
 }
 
+fn parse_elementdecl(doc: String) -> Result(#(Declaration, String), Nil) {
+  case doc {
+    "<!ELEMENT" <> tail -> {
+      use doc <- result.try(trim_mandatory_space(tail))
+      use #(name, doc) <- result.try(parse_name(doc))
+      use doc <- result.try(trim_mandatory_space(doc))
+      case doc {
+        "EMPTY" <> tail -> {
+          let doc = trim_space(tail)
+          case doc {
+            ")" <> tail -> {
+              Ok(#(ElementDecl(name, Empty), tail))
+            }
+            _ -> Error(Nil)
+          }
+        }
+        "ANY" <> tail -> {
+          let doc = trim_space(tail)
+          case doc {
+            ")" <> tail -> {
+              Ok(#(ElementDecl(name, Any), tail))
+            }
+            _ -> Error(Nil)
+          }
+        }
+        "(" <> _ -> {
+          try_parsers([parse_mixed(name, _), parse_children(name, _)], doc)
+        }
+        _ -> Error(Nil)
+      }
+    }
+    _ -> Error(Nil)
+  }
+}
+
+fn parse_children(
+  name: String,
+  doc: String,
+) -> Result(#(Declaration, String), Nil) {
+  use #(children, doc) <- result.try(try_parsers([parse_choice, parse_seq], doc))
+
+  let #(children, doc) = case doc {
+    "?" <> tail -> {
+      #(set_optional(children, ZeroOrOne), tail)
+    }
+    "*" <> tail -> {
+      #(set_optional(children, ZeroOrMore), tail)
+    }
+    "+" <> tail -> {
+      #(set_optional(children, OneOrMore), tail)
+    }
+    _ -> {
+      #(children, doc)
+    }
+  }
+  children |> echo
+  doc |> echo
+  todo
+}
+
+fn parse_choice(doc: String) -> Result(#(ContentParticle, String), Nil) {
+  case doc {
+    "(" <> tail -> {
+      let doc = trim_space(tail)
+      use #(cp, doc) <- result.try(parse_cp(doc))
+      use #(cps, doc) <- result.try(case do_parse_choice(doc, [cp]) {
+        Ok(#(ChoiceParticle([], _), _))
+        | Ok(#(ChoiceParticle([_], _), _))
+        | Error(_) -> Error(Nil)
+        Ok(#(cps, doc)) -> Ok(#(cps, doc))
+      })
+      let doc = trim_space(doc)
+      case doc {
+        ")" <> tail -> Ok(#(cps, tail))
+        _ -> Error(Nil)
+      }
+    }
+    _ -> Error(Nil)
+  }
+}
+
+fn do_parse_choice(
+  doc: String,
+  acc: List(ContentParticle),
+) -> Result(#(ContentParticle, String), Nil) {
+  let doc = trim_space(doc)
+  case doc {
+    "|" <> tail -> {
+      let doc = trim_space(tail)
+      use #(cp, doc) <- result.try(parse_cp(doc))
+      do_parse_choice(doc, [cp, ..acc])
+    }
+    _ -> Ok(#(ChoiceParticle(list.reverse(acc), One), doc))
+  }
+}
+
+fn parse_seq(doc: String) -> Result(#(ContentParticle, String), Nil) {
+  case doc {
+    "(" <> tail -> {
+      let doc = trim_space(tail)
+      use #(cp, doc) <- result.try(parse_cp(doc))
+      let #(cps, doc) = case do_parse_seq(doc, [cp]) {
+        Ok(#(cps, doc)) -> #(cps, doc)
+        Error(_) -> #(SeqParticle([cp], One), doc)
+      }
+      let doc = trim_space(doc)
+      case doc {
+        ")" <> tail -> Ok(#(cps, tail))
+        _ -> Error(Nil)
+      }
+    }
+    _ -> Error(Nil)
+  }
+}
+
+fn do_parse_seq(
+  doc: String,
+  acc: List(ContentParticle),
+) -> Result(#(ContentParticle, String), Nil) {
+  let doc = trim_space(doc)
+  case doc {
+    "," <> tail -> {
+      let doc = trim_space(tail)
+      use #(cp, doc) <- result.try(parse_cp(doc))
+      do_parse_seq(doc, [cp, ..acc])
+    }
+    _ -> Ok(#(SeqParticle(list.reverse(acc), One), doc))
+  }
+}
+
+fn parse_cp(doc: String) -> Result(#(ContentParticle, String), Nil) {
+  use #(el, doc) <- result.try(try_parsers(
+    [
+      fn(doc) {
+        use #(name, doc) <- result.try(parse_name(doc))
+        Ok(#(ElParticle(name, One), doc))
+      },
+      parse_choice,
+      parse_seq,
+    ],
+    doc,
+  ))
+
+  case doc {
+    "?" <> tail -> {
+      Ok(#(set_optional(el, ZeroOrOne), tail))
+    }
+    "*" <> tail -> {
+      Ok(#(set_optional(el, ZeroOrMore), tail))
+    }
+    "+" <> tail -> {
+      Ok(#(set_optional(el, OneOrMore), tail))
+    }
+    _ -> {
+      Ok(#(el, doc))
+    }
+  }
+}
+
+fn set_optional(el: ContentParticle, optional: Optional) -> ContentParticle {
+  case el {
+    ChoiceParticle(choices, _) -> ChoiceParticle(choices:, optional:)
+    ElParticle(name, _) -> ElParticle(name:, optional:)
+    SeqParticle(seq, _) -> SeqParticle(seq:, optional:)
+  }
+}
+
+fn parse_mixed(name: String, doc: String) -> Result(#(Declaration, String), Nil) {
+  case doc {
+    "(" <> tail -> {
+      let doc = trim_space(tail)
+      case doc {
+        "#PCDATA" <> tail -> {
+          use #(els, doc) <- result.try(parse_mixed_elements(tail))
+          let doc = trim_space(doc)
+          case els {
+            [] -> {
+              case doc {
+                ")*" <> tail ->
+                  Ok(#(ElementDecl(name, Mixed(["#PCDATA"])), tail))
+                _ -> Error(Nil)
+              }
+            }
+            _ -> {
+              case doc {
+                ")" <> tail ->
+                  Ok(#(ElementDecl(name, Mixed(["#PCDATA", ..els])), tail))
+                _ -> Error(Nil)
+              }
+            }
+          }
+        }
+        _ -> Error(Nil)
+      }
+    }
+    _ -> Error(Nil)
+  }
+}
+
+fn parse_mixed_elements(doc: String) -> Result(#(List(String), String), Nil) {
+  Ok(
+    parse_multiple_to_list(
+      doc,
+      fn(doc) {
+        let doc = trim_space(doc)
+        case doc {
+          "|" <> tail -> {
+            let doc = trim_space(tail)
+            parse_name(doc)
+          }
+          _ -> Error(Nil)
+        }
+      },
+      [],
+    ),
+  )
+}
+
 fn get_entity_replacement(
   entity: String,
   decl_list: List(Declaration),
@@ -537,10 +788,10 @@ fn get_entity_replacement(
 }
 
 fn parse_external_id(doc: String) -> Result(#(Option(ExternalID), String), Nil) {
-  let doc = trim_space(doc)
+  use doc <- result.try(trim_mandatory_space(doc))
   case doc {
     "SYSTEM" <> tail -> {
-      let doc = trim_space(tail)
+      use doc <- result.try(trim_mandatory_space(tail))
       use #(system_literal, doc) <- result.try(parse_system_literal(
         doc,
         None,
@@ -549,13 +800,13 @@ fn parse_external_id(doc: String) -> Result(#(Option(ExternalID), String), Nil)
       Ok(#(Some(SystemID(system_literal:)), doc))
     }
     "PUBLIC" <> tail -> {
-      let doc = trim_space(tail)
+      use doc <- result.try(trim_mandatory_space(tail))
       use #(public_literal, doc) <- result.try(parse_public_literal(
         doc,
         None,
         "",
       ))
-      let doc = trim_space(doc)
+      use doc <- result.try(trim_mandatory_space(doc))
       use #(system_literal, doc) <- result.try(parse_system_literal(
         doc,
         None,
@@ -695,11 +946,11 @@ fn parse_misc(doc: String) -> String {
     try_parsers(
       [
         parse_comment,
+        parse_pi,
         fn(doc) {
           parse_space(doc)
           |> result.map(fn(sp) { #(Whitespace, sp.1) })
         },
-        parse_pi,
       ],
       doc,
     )
@@ -729,8 +980,8 @@ fn parse_decl(doc: String) -> Result(#(Declaration, String), Nil) {
 }
 
 fn parse_versioninfo(doc: String) -> Result(#(String, String), Nil) {
-  case trim_space(doc) {
-    "version=" <> tail -> {
+  case trim_mandatory_space(doc) {
+    Ok("version=" <> tail) -> {
       use #(version, doc) <- result.try(parse_version(tail))
       Ok(#(version, doc))
     }
@@ -770,8 +1021,8 @@ fn do_parse_version(
 }
 
 fn parse_encodingdecl(doc: String) -> Result(#(String, String), Nil) {
-  case trim_space(doc) {
-    "encoding=" <> tail -> {
+  case trim_mandatory_space(doc) {
+    Ok("encoding=" <> tail) -> {
       case tail {
         "\"" <> tail -> {
           use #(encoding, doc) <- result.try(parse_encoding(tail))
@@ -821,10 +1072,11 @@ fn parse_encoding(doc: String) -> Result(#(String, String), Nil) {
 }
 
 fn parse_standalone(doc: String) -> Result(#(Bool, String), Nil) {
-  case trim_space(doc) {
-    "standalone=\"yes\"" <> tail | "standalone='yes'" <> tail ->
+  case trim_mandatory_space(doc) {
+    Ok("standalone=\"yes\"" <> tail) | Ok("standalone='yes'" <> tail) ->
+      Ok(#(True, tail))
+    Ok("standalone=\"no\"" <> tail) | Ok("standalone='no'" <> tail) ->
       Ok(#(True, tail))
-    "standalone=\"no\"" <> tail | "standalone='no'" <> tail -> Ok(#(True, tail))
     _ -> Error(Nil)
   }
 }
@@ -1053,6 +1305,18 @@ fn parse_name_char(doc: String) -> Result(#(String, String), Nil) {
   }
 }
 
+fn trim_mandatory_space(doc: String) -> Result(String, Nil) {
+  do_trim_mandatory_space(doc, True)
+}
+
+fn do_trim_mandatory_space(doc: String, first: Bool) -> Result(String, Nil) {
+  case parse_space(doc), first {
+    Ok(#(_, doc)), _ -> do_trim_mandatory_space(doc, False)
+    Error(_), True -> Error(Nil)
+    Error(_), False -> Ok(doc)
+  }
+}
+
 fn trim_space(doc: String) -> String {
   case parse_space(doc) {
     Ok(#(_, doc)) -> trim_space(doc)
@@ -1094,6 +1358,21 @@ fn parse_multiple(
   }
 }
 
+fn parse_multiple_to_list(
+  to_parse str: String,
+  with to_run: fn(String) -> Result(#(String, String), Nil),
+  acc ret: List(String),
+) -> #(List(String), String) {
+  case str {
+    "" -> #(list.reverse(ret), str)
+    _ ->
+      case to_run(str) {
+        Ok(#(r, rest)) -> parse_multiple_to_list(rest, to_run, [r, ..ret])
+        Error(_) -> #(list.reverse(ret), str)
+      }
+  }
+}
+
 fn parse_multiple_optional(
   to_parse str: String,
   with to_run: fn(String) -> Result(#(String, String), Nil),