no object returned

I would like to run the following query :
List the reserves of those open auctions where a certain person issued a bid before another person.

I write this query in X-Query as

/site/open_auctions/open_auction[bidder/personref/@person = “person18829” before bidder/personref/@person = “person10487”]/reserve

However,it returns no object. Is something wrong with my query (I am using Tamino

I have another question related with queries returning large results. When I run such queries using Interactive Interface, first results are displayed in a short time but it takes too long to return the whole result. What can I do?

The left operand of the before or after operator must be a set of sibling nodes and the right-hand operand must be an element of this node-set (otherwise an empty node-set will be returned as a result).

Example of after is like that
(/Hasta/Kimlik/Adres/* after Il) [//AcikAdres ~= “Ye?ilbahar” ]

another example
/Hasta/Kimlik [Adres/AcikAdres ~= “Ye?ilbahar” adj “sok” ]
But these are not match in your case
Try this one
/Hasta/Kimlik [Telefon ~= “21*” ] after //Telefon [//Telefon ~=“533”]