You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Utrecht

Context:
When the Frankish rulers established the system of feudalism, the Bishops of Utrecht came to exercise worldly power as prince-bishops. The territory of the bishopric not only included the modern province of Utrecht (Nedersticht, 'lower Sticht'), but also extended to the northeast. The feudal conflict of the Middle Ages heavily affected Utrecht. The prince-bishopric was involved in almost continuous conflicts with the Counts of Holland and the Dukes of Guelders. The Veluwe region was seized by Guelders, but large areas in the modern province of Overijssel remained as the Oversticht.

Question:
Who was in conflict with the prince bishopric 

the Counts of Holland and the Dukes of Guelders