The most common forms of Sufi group dhikr consist in the recital of particular litanies (e.g. Hizb al-Bahr of the Shadhilis), a composition of Quranic phrases and Prophetic supplications (e.g. Wird al-Latif of the Ba `Alawis), or a liturgical repetition of various formula and prayers (e.g. al-Wadhifa of the Tijanis ). All of these forms are referred to as a "hizb" ("pl." "ahzab") or a "wird" ("pl." "awrad"). This terminological usage is important as some critics often mistakenly believe that the word hizb only refers to a portion of the Quran. In addition, many recite extended prayers upon Muhammad (known as durood) of which the Dala'il al-Khayrat is perhaps the most popular. Though common to almost all Sufi orders, some (such as the Naqsbandis) prefer to perform their dhikr silently - even in group settings. In addition, most gatherings are held on Thursday or Sunday nights as part of the institutional practices of the tariqah (since Thursday is the night marks the entrance of the Muslim "holy" day of Friday and Sundays are a convenient congregational time in most contemporary societies) - though people who don't live near their official zawiya gather whenever is convenient for the most people.