I am trying to display the attribute of the parent object (Proposal) on my child object (Line Item) edit page.  However, I can't seem to figure out the proper syntax or way to make this call.   I continue to get a message stating Unknown property 'Line_Items__cStandardController.Proposal__r'.  Any thoughts on how I can fix the line higlighted below?  Thanks!

<apex:page standardController="Line_Items__c" sidebar="true">
    <apex:sectionHeader title="Edit Proposal Line Item" subtitle="{!Line_Items__c.name}"/>
        <apex:form >
            <apex:pageBlock title="Edit Proposal Line Item" id="thePageBlock" mode="edit">
                 <apex:pageBlockButtons >
                    <apex:commandButton value="Save" action="{!save}"/>
                    <apex:commandButton value="Cancel" action="{!cancel}"/>                 
                  </apex:pageBlockButtons>
          <apex:actionRegion >
                <apex:pageBlockSection title="Basic Information" columns="1">
                     <apex:inputField value="{!Line_Items__c.Proposal__c}"/>
                       <apex:pageBlockSectionItem >
                             <apex:outputLabel value="Type"/>
                                 <apex:outputPanel >
                                     <apex:inputField value="{!Line_Items__c.Type__c}">
                                        <apex:actionSupport event="onchange" rerender="thePageBlock" status="status"/>
                                     </apex:inputField>
                                     <apex:actionStatus startText="applying value..." id="status"/>
                                 </apex:outputPanel>
                        </apex:pageBlockSectionItem>
                 </apex:pageBlockSection>

             </apex:actionRegion>
             <apex:pageBlockSection title="Platform Access and Initial Setup" columns="1"
             rendered="{!Line_Items__c.Type__c == 'Platform Access and Initial Setup'}">
                 <apex:outputText value="Based on the launch model selected, input the corresponding cost listed below into the Actual Cost field."/>
                   <apex:outputText value="Shared Cost = $10,000"/>
                   <apex:outputText value="Dedicated Cost = $20,000"/>
               </apex:pageBlockSection>
          <apex:pageBlockSection title="Application AHMS" columns="1"
             rendered="{!Line_Items__c.Type__c == 'Application AHMS'}">
                    <apex:outputField value="{!Line_Items__c.Proposal__c}"/>
                   <apex:inputField value="{!Line_Items__c.Application__c}"/>
                    <apex:outputField value="{!Line_Items__c[Proposal__r]['Calculated_Site_Equivalents__c']}"/>
                   <apex:inputField value="{!Line_Items__c.Actual_Site_Equivalents_Used__c}"/>
                   <apex:inputField value="{!Line_Items__c.Suggested_Price__c}"/>
               </apex:pageBlockSection>
             <apex:pageBlockSection columns="1">
                  <apex:inputfield value="{!Line_Items__c.Actual_Cost__c}"/>
             </apex:pageBlockSection>
         </apex:pageBlock>
     </apex:form>
</apex:page>