Filter SalesOrders on ItemType - Write Measures

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Looking to write measures based on sales orders that contain a certain type of item. I have a sales order table with lines for each item within a sale and then an items table that are related based on the ItemID. What I want to do is filter out the sales orders that do not have a "core" item, which is identified on the items table, but include all products (even non-core ones) associated on that sales order. 

So "does this sales order contain a core item? Yes? Ok here are all the sales orders for that and everything that's in them." 

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