were true. The fact that Zhongshan was invited to the five state alliance is seen as another proof of them being Chinese, as a barbarian (Yi) country would never be invited to such an alliance. After this, King Wei of Qi asked Wei and Zhao to join him in attacking Zhongshan, to force them to abolish their title of wang, however, King Cuo sent an advisor, Zhang Deng, to these states, and successfully sowed discord and distrust amongst them, and no such alliance was formed. Zhao The state of Zhao surrounded Zhongshan almost entirely, with only Zhongshan's northeastern border being outside of Zhao. For this reason, they were considered to be a "disease in the heart and belly" by the Zhao kings. From 307 BC on, Zhao attacked Zhongshan almost every year, until, in 301, the king of Zhongshan was forced to take refuge in Qi. During this time Qi declared war on and invaded Chu; seeing that Qi was occupied with a war of their own, Zhao pushed deep into Zhongshan, and fully conquered them. Economy Due to commonality of finds of iron agricultural tools in the southern part of Zhongshan, compared to the commonality of animal skeletons in the northern part, it is believed that the southern land's economy was mostly agriculture, and the northern land's was mostly from animal husbandry. Currency Zhongshan used a currency called chengbo, which took the form of a 15 gram bronze knife shaped coin. It is known that these coins were made in at least Lingshou. The level of trade, and the relationship, Zhongshan had with other states can be roughly ascertained from the amount of a currency was found in the ruins of Lingshou: the yan knife coins from Yan were plentiful, with some 374 being found, whereas the gandan, baihua, and lin coins of Zhao are rare, with only 100 of them, combined, found. This reflects the hostile relations Zhao had with Zhongshan, and the good relations Yan had with Zhongshan. Indeed, even the similarities of the yan and chengbo knife coins seems to suggest their friendly relationship, as they were of similar size and of equal weight, with both weighing fifteen grams, meaning that they would be interchangeable. Archeology and culture Much of the knowledge of Zhongshan architecture comes from the remains of their capital city, Lingshou, and from the tombs of King Cheng, and his son King Cuo.