▁have ▁also ▁been ▁ ▁and ▁, ▁as ▁in ▁modern ▁Dutch . ▁▁ ▁was ▁a ▁back ▁ ▁in ▁most ▁vari eties , ▁but ▁front ▁ ▁probably ▁occurred ▁in ▁some ▁western ▁dialect s . ▁ ▁Long ▁v ow els ▁and ▁di ph th ongs ▁Long ▁v ow els ▁and ▁di ph th ongs ▁cannot ▁be ▁clearly ▁distinguished ▁in ▁Middle ▁Dutch , ▁as ▁many ▁long ▁v ow els ▁had ▁or ▁developed ▁a ▁di ph th ong al ▁quality , ▁while ▁existing ▁di ph th ongs ▁could ▁also ▁develop ▁into ▁mon op ht ongs . ▁Sometimes , ▁this ▁occurred ▁only ▁in ▁restricted ▁dialect s , ▁other ▁develop ments ▁were ▁w ides p read . ▁▁ ▁The ▁rounded ▁front ▁v ow els ▁in ▁brackets ▁only ▁occurred ▁in ▁the ▁eastern ▁dialect s , ▁where ▁um la ut ▁of ▁long ▁v ow els ▁and ▁di ph th ongs ▁occurred . ▁ ▁The ▁rounded ▁back ▁v owel ▁ ▁only ▁occurred ▁in ▁the ▁Lim burg ish ▁dialect s . ▁ ▁Many ▁details ▁of ▁the ▁exact ▁ph on et ics ▁are ▁uncertain , ▁and ▁seemed ▁to ▁have ▁differ ed ▁by ▁dialect . ▁The ▁overall ▁system ▁is ▁clear , ▁however , ▁as ▁almost ▁all ▁the ▁v ow els ▁remain ▁distinct ▁in ▁modern ▁Lim burg ish : ▁, ▁, ▁, ▁ ▁and ▁ ▁appear ▁in ▁modern ▁Lim burg ish ▁as ▁, ▁, ▁, ▁ ▁and ▁ ▁respectively . ▁ ▁The ▁v ow els ▁, ▁ ▁and ▁ ▁developed ▁from ▁Old ▁Dutch ▁opening ▁di ph th ongs , ▁but ▁their ▁exact ▁character ▁in ▁Middle ▁Dutch ▁is