Sweden The monarchy in Sweden has had several periods of joint rule: Erik and Alrik, Yngvi and Alf, Björn at Hauge and Anund Uppsale, Eric the Victorious and Olof Björnsson, Eric the Victorious and Olof Skötkonung, Halsten Stenkilsson and Inge I, and Philip and Inge II. Vietnam Coregency is a special feature of the Trần dynasty, in which a senior king abdicated in favor of his chosen heir. This abdication, however, is only in name, as the abdicated king continued to rule while his successor sat on the throne as a learner. China Co-regency was common amongst the Chinese ethnics both formally or informally dating far back to the Han Dynasty to the Late Qing dynasty, if it happened to be so that a new Emperor ascended the throne and was mature but not well adept with politics, it was a national concern for stability in which the monarch was the head of State de-jure whereas a co-regent was its de-facto ruler. The requirements for the position of co-regent depended on the power of an individual along with their ability to command the Confidence of the Parliament and it could be an official in the Imperial Court, a close and trustworthy paternal or maternal relative or the most appropriate being the Most Senior Member of the Imperial family in the Palace which was either the Grand Empress Dowager or the Empress Dowager. The absence of all these specific personalities could rarely pave way for the monarch's wife if she seemed more competent. The most outstanding co-regencies were those of Empress Wu Zetian during the Tang Dynasty in the reign of her husband that Gaozong Emperor even if it was informal, the Empress Dowager Xiang became co-regent for the Emperor Huizong of Song, her adopted son in 1100 while the Grand Empress Dowager Wu became co-regent of the Emperor Guangzong of Southern Song in the year 1189 even if his Empress Li Fengniang later posthumously honored as Ciyi became the de-facto ruler, Empress Dowager Yang served as co-regent of the Emperor Lizong from 1224 until her death in 1233 even if she soon surpassed his own influence and ruled ultimately like an Empress Regnant even if she was never actually one. During the Qing Dynasty the Empress Dowagers Ci'an of the Manchu Niohuru clan along with Ci'xi of the Manchu Yehenara clan served as Co-regents from 1861 until Ci'an's death in